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Understand and make the most of PDF
Acrobat PDF is one of the most important and most versatile of all file formats. Probably most users' first experience of PDF will have been as an electronic replacement for a printed software manual, but the format keeps cropping up in different contexts. Other common uses include acting as the underlying medium for Web-based publications, downloadable eBooks, onscreen presentations, office collaboration, legally-binding document exchange, commercial print workflows and electronic archiving. PDF can even act as a graphic file standard for both bitmap photo-editing and vector drawing programs!
Most users' first experience of PDF is as an electronic replacement for a printed manual.
This multi-faceted nature of Acrobat is its greatest strength but it's also a serious drawback - PDF is clearly powerful but just what is it exactly? The very name "Acrobat" and its juggler logo suggest flexibility and the ability to keep several balls in the air simultaneously, but that hardly helps to pin the format down. The full title of the technology, Portable Document Format, gives more of a clue in that Acrobat is primarily used as a medium for exchanging documents, but then so are Office files. Recently though Adobe has come up with a term that really does encapsulate what Acrobat is all about - "ePaper". What makes Acrobat unique is its ability to act as an electronic equivalent of the printed page.
Of course the ability to print a document is hardly exceptional, so to really understand what makes PDF different, it's necessary to look more closely at the format's fundamental link to paper and at its underlying architecture. Ultimately what makes PDF so powerful is that it is built on PostScript. PostScript is a Page Description Language (PDL), a programming language optimised to accurately describe the layout and visual appearance of a page including all vectors, bitmaps and, crucially, fonts. Effectively PostScript works by recreating each page as a program that can in turn recreate the page on any PostScript-supporting device.
PDF is based on Adobe's PostScript PDL.
This has a number of crucial advantages. To begin with PostScript is platform-independent as its ASCII-based text files can be handled just as easily on a PC, Mac or Unix workstation. Secondly PostScript is application-independent as, once you've installed a PostScript driver, you can produce a PostScript file from the Print command of any application (though for colour-separated artwork you'll need a dedicated PostScript-friendly application). Finally, PostScript is device-independent which means that you'll get exactly the same page layout produced on a 400-dpi (dots per inch) PostScript laser as you will on a 4000-dpi imagesetter - the only difference will be the resolution and quality.
These three advantages have turned PostScript into the architecture that dominates the entire commercial publishing industry, but there's one fundamental flaw - the system only works with PostScript devices. And that immediately means that the majority of office lasers and inkjets aren't compatible. More importantly the display device of the computer itself, the monitor, is outside the PostScript loop so that you can't actually see what the PostScript-defined page looks like until it is printed.
Adobe recognised that if it could solve this problem and close the loop, PostScript would prove invaluable not just in the publishing industry but also in the even larger office-based market. The solution it came with - after a failed attempt to push the OS-level, screen-oriented DisplayPostScript technology - was Acrobat and the PDF file format. PDF is still built on the same programmatic imaging model as in PostScript - as you can see if you open an uncompressed PDF in a text editor - but the PostScript is in an optimised format which has been pre-interpreted for rapid onscreen display.
To enable this all-important display, along with the PDF format, Adobe launched the Reader program that lets you load and view PDFs and print them to any printer. It was this freely-distributable cross-platform Reader program that was Acrobat's great selling point. At the time the computer world was riven with incompatibilities between platforms such as PC, Mac and Unix, and applications such as Word, WordPerfect and AmiPro. The end result was that, if you were lucky enough to be able to read someone else's file, the font information would certainly be different and so would the printed layout. In other words, each time someone looked at a document it would be different!
The free Acrobat Reader program is available from the Adobe Web site and most cover CDs.
Suddenly thanks to PDF's PostScript-inherited strengths, these problems were solved. With Acrobat, users could easily share information created on any platform with any application and, if desired, be sure of printing exactly the same layout to any printer. The potential of using PDF as the lingua franca of computer applications was enormous and Adobe evangelised the idea of the "paperless office" built on the fast electronic distribution of free-to-produce, full-colour PDFs rather than the existing slow, expensive and largely monochrome paper trail.
Things didn't quite work out as Adobe expected. The OS and application developers addressed the worst problems of platform and application incompatibility while the increasing dominance of, and convergence on, Microsoft Office meant that workgroups could easily work together on the same documents. If you can share editable DOC files, why bother with fixed PDFs? At the same time the development of HTML and the Web provided an even more efficient electronic means of publishing and sharing information.
Adobe's vision of the paperless office built on Acrobat proved unrealistic but PDF found new roles for itself, ironically by emphasizing its central tie-in to paper print. In the office, for example, PDF's lack of serious editability and its fixed layout becomes a serious advantage when working on a publication destined for print or archiving (see this month's RW column). On the Web too, PDF found a new purpose when Acrobat turned the Reader program into a plug-in enabling the Web browser to open, view and print high-impact publications that left the design-limited HTML for dead. Eventually Adobe also recognised the apparently obvious potential of using PDF as a PostScript replacement for reliably producing commercial print.
Acrobat files can be seamlessly mixed with HTML pages on the Web.
Acrobat isn't the panacea that Adobe first envisaged but it's still a central format with unmatchable strengths for workgroups, web designers and print-based publishers. At its best it covers all three acting first as the means for ongoing collaboration and then as the route to reliable, worry-free commercial print and to instant, cost-free Web publishing.
Creating - Distiller
We now know what Acrobat is, where it came from and what it does - now let's see how we can put it to work and make the most of it. The first step of course is to actually create the PDF. There are various third-party options for this, such as 5D (formerly Niknak) and Easy PDF, and high-end PostScript-savvy applications from Corel Draw through to Quark XPress are increasingly providing in-built PDF export. However there are strong arguments for sticking with those who know the format best and for the vast majority of users this means moving up from the free Reader program and paying for Adobe's full Acrobat 5 suite.
In the past the quickest way to create your PDF was to use the PDFWriter printer driver that came with Acrobat and which was available from any application's Print dialog. However this approach dated from the early paperless-office days of Acrobat and so used Window's own comparatively under-powered printing model. Nowadays the PDFWriter/GDI route has been deprecated in favour of a full PostScript-based workflow.
As such the most important program in the Acrobat suite is the unprepossessing Distiller utility that takes a PostScript print-to-disk file and converts the serial PostScript flow into the pre-interpreted, object-oriented and page-independent PDF. Adobe recognises that this two-step process isn't exactly intuitive and so offers a number of alternatives for creating PDFs more directly including a Distiller-based virtual printer driver available from any application and a Create Adobe PDF macro available from Office applications.
It might not look like much, but Distiller is the key to producing PDFs.
In each case the process might seem more direct, but ultimately behind-the-scenes it still uses exactly the same PostScript-based route so, if you really want to make the most of your PDF workflows, your best option is to get to grips with Distiller. And the reason that you have to understand what Distiller does rather than just let it get on with it, is because there are different flavours of PDF optimised for different purposes.
The bad news is that there are around fifty parameters in Distiller's Job Settings dialog that can radically change or subtly fine-tune each PDF that you create. The good news is that all these settings tend to fall into just three main camps depending on the final intended use of the PDF. And each of these three camps is based on the main target users that we've already identified - office workgroups, web designers and print designers. Even better Distiller lets you quickly target each of these groups with presets available directly from the Job Options dropdown in its main dialog.
Distiller's Job Options let you target your PDF for different uses.
The presets are an excellent starting point but it's worth exploring each option in more detail to understand how and why they differ. If you select Acrobat 5's default preset, now called "eBook", and then look at the different Compression, Fonts and Colour tabs of the Job Options dialog (Ctrl+J) you'll see that high-resolution colour and grayscale images have been set to be downsampled to 150 dpi and monochrome images to 300dpi, all fonts are set to be automatically embedded apart from the 14 base set that are built-in to Acrobat, and all colours are converted to the sRGB standard. These are the defaults to create a PDF that is easily exchangeable while displaying and, where necessary printing, to a more than acceptable standard on the average computer set-up - in other words ideal for most office use.
If you look at the "Screen" preset's job options, you'll see that the settings are very different. Again all fonts apart from the 14 base typefaces are set to embed and this time colours are converted to the older calRGB standard. More significantly, colour and grayscale images are now set to be downsampled to 72dpi and monochrome images to 300dpi. Most significant of all, under the General setting, you'll see that the PDF format is set to Acrobat 3's 1.2 standard to ensure maximum backward-compatibility. The aim here is to produce the most widely viewable PDF with the smallest possible file size for easy Web delivery.
If you look at the "Press" preset you'll see that things are different again. Here all fonts including the base 14 are set to embed and all colours are left unchanged as it's assumed that you will have set up your own colour management (the alternative "Print" preset is almost identical to the Press option but with colour management tagging designed for digital print and client proofing). Compression is still set on but images are only down-sampled if they are over 300dpi for colour and grayscale images and 1200dpi for monochrome images which provides sufficient resolution for the highest-quality imageset output. You'll also see that other prepress settings for managing features such as overprinting and job tickets are set to on. For press use, file size is less of an issue compared to ensuring that all the information necessary for successful commercial print is present.
Being familiar with Distiller's Job Options lets you take absolute control, for example if you want to preserve a halftone effect that you've applied in your DTP program or to embed an entire font not just a subset. Generally though you only need to understand that the main presets represent a different mix of information stored and resulting file size and therefore a different target use: Screen for web publishing, Press/Print for commercial print and eBook for everything in-between.
Making the Most - Acrobat
Now we know how the underlying PostScript is distilled to create PDFs, the next stage is to see just how versatile the format can be and to see what Acrobat offers on top of its core universal viewing and printing strengths. To do this we need to move up from the free Reader program and load the full Acrobat application (see Acrobat Options boxout).
The first way in which Acrobat adds value is by enabling the PDF author to add value for their end users. Using the commands under the Document menu you can delete unnecessary pages, crop unwanted margins and insert pages from other PDFs, rotating them if necessary. You can also set up page numbering so that the page number shown in Acrobat's status bar matches the numbering of the sections in the actual document.
You can also improve the onscreen reading experience by selecting any section of text with the Text Select tool, right-clicking and choosing New Bookmark. The marked text is automatically added to the Bookmarks navigation panel and clicking on it will instantly take the end user to the marked spot and at the currently selected zoom level. If your document contains multiple stories in a multi-column layout or split through a document, you can also use the Article tool to mark up the flow of text so that it's easier to follow a story through - though inevitably this remains slightly awkward (see Screen v Page boxout).
One area where electronic publications shine compared to their paper equivalents is hypertext, with the ability to jump from one reference to another. Using Acrobat's dedicated Link tool and dialog you can set up internal links much like you set up bookmarks by navigating through a document and setting the desired view - you can even set up links to other PDFs simply by opening the file and navigating to the desired location. Alternatively, you can add simple Forward, Back and Go To buttons or, using the World Wide Web link option, you can set a destination URL that will load into the user's browser.
By adding bookmarks and links you can boost your PDF's navigability.
Manually enhancing PDFs in this way is useful but laborious. A major improvement is the Tools>Locate Web Addresses command which automatically converts any http addresses to links but the system's still not very intelligent or flexible. Usually it's far better to set up all features such as tables of contents, cross-references, index entries, URLs and so on, in your DTP or WP package and then automatically convert them to PDF bookmarks and links. Such in-depth support is now common in high-end design-based packages, especially those from Adobe, but you don't need to spend a fortune. Thanks to Acrobat's PDFMaker macro available from Microsoft Office applications, Word makes a very capable PDF author for producing electronic publications for onscreen reading.
While it's generally a good idea to do as much as possible to prepare your PDF in your originating package, there's one enhancement that only Acrobat offers - the ability to add multimedia elements. Using the Link tool and a little lateral thinking you can create a link that automatically plays an embedded WAV file when it is clicked. Alternatively, using the dedicated Movie tool, you can place a MOV or AVI video on your page. The movie files aren't stored internally so you'll have to remember to include them on your CD or use the Remote URL option for Web delivery, but you can embed a poster image taken from the movie.
Using the Link and Movie tools you can create multimedia publications.
You can also enhance the end-user experience of your project by using the Document Properties>Open Options setting to specify that the PDF should open in Full Screen mode so that allthat is visible is the page. Using the Preferences>General>Full Screen settings the end user can then control looping, page advance and transitions and even disable the Escape key to create a kiosk-style presentation. Acrobat can't compete with the likes of Director for state-of-the-art multimedia and its projects are intrinsically page rather than screen-based, but this ability to turn output from any application into an impressive onscreen presentation is generally under-appreciated.
As well as enabling you to put more into your PDFs, the Acrobat application also enables you to get more out. This added functionality tends to fall into the three main target areas of workgroup users and Web and print designers.
For workgroups Acrobat offers a dedicated Commenting toolbar with no less than 14 options for adding lines, circles, rectangles, stamps and Post-It-style notes and for adding, highlighting, underscoring and striking out text. There's even an in-built recorder so that you can add voice comments. Using the Tools menu commands you can then find, filter and summarize the comments and even compare two versions of the same document and automatically generate an annotated version highlighting the differences.
Comments and secure digital signatures are ideal for collaborative and approval-based workflows.
The big drawback of Acrobat's comments-based collaborative system is that to make any changes you have to go back to the originating application armed with your PDF printout. This lack of editability and flexibility is often a drawback but at other times the PDF's fixed page-based nature is a strength, for example when you're working on layouts destined for print. Another important benefit of the PDF's fixed nature is the ability to make it secure. At the simplest level you can set a password for opening a PDF and at the same time control the end users' ability to edit, copy and print it once opened. You can also choose either 40-bit or industrial-strength 128-bit encryption, though the latter is only supported in the latest PDF 1.4 format.
Rather than passwords you can instead use Acrobat's certificate-based security, either the Self-Sign system that Adobe provides or one of many third-party systems such as Entrust and Verisign. This has two benefits as you can safely and transparently exchange PDFs within a closed certificated workgroup and you can also electronically and securely sign a PDF with the Digital Signature tool. This ability to sign a fixed PDF is crucial for work where responsibility needs to be established - signed Acrobat files are now accepted in court in some countries. However we've yet to see whether the Sklyarov case's highlighting the security flaws in Acrobat's eBook-based security system affects the format's legal acceptance.
Acrobat's electronic nature makes it well suited for document exchange, and the File>Send Mail command makes it particularly simple to send the currently open PDF, but it's even better suited to Web delivery. Effectively all you have to do is post a single Screen-optimised PDF to a Web server and suddenly your high-impact full-colour publication is universally and instantly available - and at no cost! Even better, thanks to its hypertext capabilities and as the Reader program operates as a browser plug-in, your site can relatively seamlessly combine HTML-based pages optimised for onscreen browsing and fully-designed PDF pages optimised for printing and for archiving. Acrobat even offers its excellent Web Capture command to enable you to store Web pages and whole sites as a single self-contained PDF archive.
Acrobat's Web Capture feature is ideal for archiving Web sites.
The benefits of universal Internet delivery are so enormous that it actually makes more sense for a workgroup to add its comments to a single server-based PDF than it does to exchange files and collate comments. That's now possible once you've set up a shared data repository via ODBC, Microsoft Office Server Extensions or as a shared network folder. You then have the ability to browse a shared copy of the PDF, pull-down existing comments and upload your own so that everyone can see what everyone else has to say about the ongoing project.
Acrobat certainly plays an important role on the Web but even here its strength ultimately derives from its page and print-oriented nature. Given this, perhaps the most obvious of all uses for Acrobat is to take advantage of its PDL foundations to provide designers with a reliable route to successful commercial print by acting as a more dependable, easily viewable, self-contained replacement for PostScript. Surprisingly though this wasn't originally on the agenda so that the initial Acrobat release was strictly limited to the RGB colourspace. Since version 3 however, Adobe has added the all-important CMYK and more recently spot colour support.
Other dedicated prepress features have followed including the Touch-Up Text tool that enables the odd word or line to be changed and the Touch-Up Object tool which lets you reposition text blocks and graphics. Thanks to its fundamentally fixed nature, PDF isn't easily editable - in particular each line stands on its own with no automatic text flow within paragraphs - but this ability to fix typos and to change addresses and dates right up until the Print command is given, is invaluable when deadlines are tight.
Another important prepress issue is accurate colour and Acrobat 5 supports the same ACE (Adobe Colour Engine) system as used in Photoshop, Illustrator and InDesign which means that embedded ICC-based colour profiles are honoured and that more dependable colour handling can be set up. It also means that you can use the View>Proof command to simulate how your publication will print on a CMYK press using coated or uncoated stock. There's also an OverPrint preview so that you can simulate how overlapping overprinting colours will actually come out.
Features like the TouchUp tools and colour management are invaluable for prepress work.
At the same time as Adobe has developed PDF as a document format, it has also been developing the format's use as a graphics standard. In particular the latest versions of Photoshop and Illustrator can save images to PDF as easily as they can to their traditional PSD and AI formats, and without sacrificing any information. The goal is clearly to make PDF the only format necessary throughout the publishing workflow - especially as PDF is also a native file format for the multi-page InDesign.
The all-PDF workflow is an exciting prospect but there's a major stumbling block to be overcome - the Acrobat application doesn't actually let you produce the colour separations necessary for commercial offset print! The end result is that many users are forced into pre-separating their work from their DTP application before distilling so that the PDF master actually contains separate pages for each cyan, magenta, yellow and black plate. Alternatively many bureaux use Acrobat's ability to export composite pages to EPS format which they then load into a program like XPress to separate. Even here though, if you've included an RGB rather than CMYK bitmap, you'll only find out when the separations are output.
These awkward workarounds are hardly the signs of the super-efficient publishing workflow that Adobe is promoting, but don't despair. To begin with there are a number of third-party utilities such as Quite a Box of Tricks and Enfocus Pitstop that can convert RGB colours to CMYK and produce colour separations. With its In-Production application, Adobe even offers these essential prepress capabilities itself - though currently only on the Mac platform.
Third-party utilities can add essential prepress capabilities but the long-term solution is hardware-based.
The real solution though isn't software- but rather hardware-based. Currently most high-end output devices are still based on PostScript Level 2 and few offer advanced features such as in-RIP separation and in-RIP trapping. This is really the problem as modern PostScript 3 devices are designed to impose, separate and even trap the composite document directly themselves. Just as importantly they are able to process PDF files directly without having to convert them back to PostScript and are able to act on PJTF (portable job ticket format) instructions within the PDF so that they can handle each print job as efficiently as possible from imposition setup through to final binding. With the right hardware in place the PDF is no longer just a useful middleman, it really can act as the one universal publishing file format right through from creative design to industrialized print.
This is the real long-term goal that Adobe has set itself with Acrobat. Any user using any application should be able to efficiently collaborate on and produce a single PDF containing any font and any graphical element. They should then be able to electronically exchange an eBook-optimised PDF or post a Screen-optimised PDF to the Web for easy onscreen reading and reliable print on any desktop printer. Alternatively by sending a Print- or Press-optimised PDF to the nearest supporting bureau they should be able to quickly, cheaply and reliably produce print-on-demand digital print-runs or colour-separated, offset print-runs of any length.
We aren't quite there yet but the benefits of such a universal publishing medium are so enormous that it's impossible to imagine that PDF won't get there eventually - especially as there's no rival format that could possibly take it on. While Acrobat's history has been patchy and its present still suffers from confusion, there's no question that its future is bright. There's a great chasm between the worlds of the computer screen and the printed page and Acrobat's ePaper solution is the only platform versatile enough to bridge the gap.
There's already considerable end-user confusion between the free Reader program and the full value-added Acrobat program (previously called Exchange) discussed in the masterclass. But now there are new variations to add to the mix. Acrobat Approval (which takes over from version 4's Acrobat Business Tools) sits somewhere between Reader and Acrobat in both price and functionality offering the commenting and security features necessary for workgroup collaboration without the authoring capability. There's also the Acrobat eBook Reader which offers dedicated features such as text-to-speech, in-built Web browsing and secure eBook purchase. Finally there are the Palm and Pocket PC versions of the free Reader designed to take PDF onto the important new territory of the handheld.
It's clear that one size doesn't fit all and some confusion is the price to be paid for Acrobat's versatility - though Adobe has hardly helped matters by seeming confused itself. Adobe's range of Acrobat applications is only the beginning however. If you visit the tool sections of www.pdfzone.com or www.planetpdf.com you'll find over five hundred third-party viewers, creators and related utilities! Ultimately Acrobat isn't a single application but rather a whole host of applications all built on the PDF platform.
Screen v Page
In the masterclass I've naturally concentrated on the strengths of the Acrobat format, but of course it's not all good news. Like every other user I tend to groan when the 500-page manual for some new piece of software is only provided as PDF. Yes I appreciate that with the PDF I've got a full-colour, searchable, annotatable, hypertext publication that doesn't eat up shelf space and that has probably shaved quite a bit of money off the software price and weeks off its launch date. The problem of course is that the PDF is just not as readable as a printed version.
Partly that's down to feeling uncomfortable taking my notebook into the bath but the real difficulty is more serious. Acrobat's fundamental tie-in with the printed page is its greatest strength but also its greatest weakness. Trying to peer at a section of a vertically-oriented, multi-column, multi-article A4 layout on a horizontally-oriented computer screen is never going to be enjoyable. And while it might be bearable on a high-resolution display, it's just not feasible on a handheld.
Tagging PDFs enables reflowable screen-based display.
Hopefully the solution is on its way. The latest Acrobat format lets you embed metadata into the PDF to tag the content that it contains. This should mean that you can mark up exactly how you want the text in the PDF page to appear when viewed in a dedicated screen mode. The necessary Reflow command is already there in Acrobat 5, what we are waiting on now are tools to take serious advantage of PDF's tagging capabilities with expectations high for the soon-to-be-released InDesign 2.
Ultimately it looks like the best way of bridging the gap between the different worlds of screen and page is to offer the best of both.
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