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PDFs - a quiet revolution
- — 02 April, 2002 12:34
The PDF format is slowly changing the way in which documents are distributed, printed and managed. "So, what exactly are PDF files, how are they produced and why is the format so successful?
PDF stands for 'Portable Document Format'. This bland name is the result of a nagging issue that has haunted computer users for years - file incompatibility. The problem still plagues users, but it was once a whole lot worse.
In the early days of word processing and desktop publishing, there were very few options for importing or exporting files between programs. This meant that if someone used one kind of word processor to produce a document, you often needed that exact program to view the file. Worse still, bonehead developers introduced file incompatibilities between some of their versions of the same program - so even if you had the correct program, you had to ensure that you were using the same version.
PC, Macintosh, OS/2 and UNIX files were notoriously incompatible. Even if you were using the same operating system, the settings on your computer may have overridden the formatting created by the document's author. Plus, if all the fonts used in the file were not installed on the end-user's computer, the result would most likely be a complete mess. Marketing people would get irate when logos shifted and colours changed or disappeared completely thanks to file incompatibility.
Finally, there is the issue of security. If you are generating electronic documents, it is important that they remain intact - you don't want to make it easy for people to change terms or conditions.
Software developer Adobe faced similar issues trying to distribute documents internally. As a result, the company devised the PDF format in 1991. In one go, PDFs fixed all these problems (and some others not mentioned here).
The idea behind the PDF process is remarkably simple and easy to imagine. When documents are sent to a printer, they are often converted to a special type of file that the printer can handle. Now imagine that instead of printing this data, you use it to generate a file. What you end up with is a fully formatted file that is independent of the program that was used to create it. This file can then be copied and used by others. It contains all the images, text and layout in a form that can be extracted when needed. All that the end-user needs is a program that can view these kinds of files. That viewer is known as the Adobe Acrobat Reader. As the name suggests, this program is only for opening/reading PDF files (you can't create PDF files with the reader).
The simplistic summary described here doesn't do justice to many of the complex processes involved in PDF files and the role of another Adobe technology - Postscript. However, few people need to worry about these intermediate steps. The Adobe site (www.adobe.com) can explain some of the finer points.
The PDF format is slowly infiltrating more and more areas and is becoming a de facto print standard.
Broadly speaking, PDFs are used in two ways: document distribution and pre-press. Pre-press involves the way files are converted and transferred from the designer's computer to a commercial printer. Pre-press is a highly specialised use of PDFs and we will not cover it here.
The area where PDF enjoys significant popularity is document distribution - particularly on the Internet. When and how to use a PDF will ultimately depend on what you are trying to achieve. At one end, the goal may simply be to produce a document for discussion, a party invitation or school assignment; at the other end lay complex engineering and legal uses, mass distribution of low-cost documents and e-books. An interesting development is the use of PDF files to submit school or university assignments to help ensure documents are not accidentally or deliberately altered.
The main function of PDF software is to convert existing files into PDF files. In many cases, the PDF software will install new buttons or menu items into your existing programs. For example, if you install Adobe Acrobat on a system with Microsoft Word, a menu toolbar will appear to allow you to create PDF files at the click of a button.
When considering PDF software, your first step should be to investigate whether you already have a PDF writer on your computer. Many design packages and business applications include a PDF creator or distiller. If you have PageMaker, Illustrator, Photoshop, InDesign, Quark XPress, Freehand, Authorware or certain software packages included with scanners, for example, you probably won't need another application.
One of the limitations to watch for when choosing a program is the resolution of the PDF. In some programs you will be given a wide range of options but others will provide only a few choices. If you are distributing simple documents via the Internet, then 72dpi is optimal. A resolution of 300dpi will produce better quality documents, but the file size will dramatically increase download times. Some packages will let you import and edit PDFs; others, however, will permit you to generate a PDF from an application but not re-import or edit the PDF.
Another feature to consider is the ability to prevent PDFs from being printed, edited or viewed by unauthorised people. Few of the cheaper, basic tools support these options and most home users would see little need for it. However, at a commercial level, the features become far more important. Note that it is a common misconception that PDF files cannot be edited: this is only true if the author has used a PDF program that has the option to restrict editing - and has used it.
The best way to find a program that has the right mix of price versus features is to take trials for a test drive. A collection of PDF programs has been included on the cover CD to help you do this. For even more options, head to PlanetPDF (www.planetpdf.com).
Trial versions present a minor annoyance - they will often print a watermark or other markings until you purchase the full version. Depending on how the watermark is added and the size of the document, this can make the files appear larger (expect about 5-10KB per page). However, the trial version will still give you the opportunity to check out the features without trying to guess how the final file will look.
Some Web sites also offer a service to create PDFs online. You simply upload your file and the Web server creates PDF files for you. Adobe has a trial of this service at https://createpdf.adobe.com and the first five PDFs are free.
The prices listed below are for single licences. Many vendors also offer volume discounts and educational prices.
If price is no object, then Adobe Acrobat is the clear choice for creating PDF files of all shapes and sizes. It also allows you to include hyperlinks, batch process files, and export the text, in addition to a host of other nifty features. However, if your objective is to simply spit out a PDF from an existing file, like a Microsoft Word document, then Acrobat is probably overkill. It doesn't have a trial version - but this is not surprising, given it's generally considered the best product on the market.
JAWS PDF Creator
JAWS PDF is a simple PDF tool that is similar to Acrobat, except most of the features have been stripped away. The result is a cheaper program that is simple to use. After installation, you can create files directly from other applications, and there is also support for 'drag and drop' for quick and painless conversions.
Developer: Global Graphics.
EasyPDF is the best-value PDF program. It includes features such as link/bookmark support, a built-in graphics editor and spell-checker. Easy PDF also has basic layout tools and the ability to import documents from RTF and DOC files (Microsoft Word must be installed). For people writing computer-related manuals, it has a handy screen-capture feature.
Developer: Visage Software.
Software602 Print Pack
The Software602 Print Pack has two main components: Print2PDF and Print2Mail. Its PDF function is very basic and there are only three resolution settings. However, it is one of the cheapest solutions for basic PDF generation.
While not related to PDFs, another feature of the Print Pack is that it can convert documents into HTML files for e-mailing.
This PDF program comes in two flavours - Standard and Pro - so you can just pay for the features you need. In both versions, you get a fairly standard set of tools, and the Pro version adds the ability to encrypt the PDF, prevent printing of the file or add password protection. Unfortunately, even the Pro version is missing the ability to add bookmarks. All up, the feature list still needs work and EasyPDF is a cheaper, more powerful alternative.
Price: Standard $US50, Pro $US100.
Acrobat 5 SDK
If you are interested in developing PDF tools, Adobe has released a Software Development Kit (SDK) for Acrobat. The 20MB download contains all of the sample code and documentation for development with the Acrobat API using C, C++, or Visual Basic (visit www.adobe.com or see the cover CD for a copy).
The pros and cons of PDFs
-PDF files can be text-searched.
-The contents of PDFs posted on Web sites are visible to search engines such as Google (www.google.com). This can help users locate a relevant document without downloading a number of unnecessary files.
-The format is generally compatible across all platforms and most setups.
-Compression techniques help keep files compact, particularly in comparison to cumbersome files generated by Word.
-Sections of a document can be bookmarked/hyperlinked.
-If the author grants permission, the text can be extracted in RTF format and used for revisions or opened in other applications.
-Compared to the large number of viruses spreading through Microsoft " Office documents, incidences of viruses in PDF files are virtually non-existent.
-As much as Adobe would like to say that the PDF format is fully compatible with just about everything, there are times when fonts are still troublesome - especially with certain printers.
-The end user still needs to install a 12MB viewer to open and print PDF files.
-There are some security issues with PDF documents, and the format is open to a range of security hacks. These typically affect password restrictions or editing rights, and are not of major concern to most users. Sensitive PDF documents should be further protected with a third-party encryption tool like PGP or Blowfish.
-Large PDFs can be difficult to open and edit.
-Even though PDFs can be searched when opened in a viewer, there is no simple way to search across multiple PDF files.
Five tips for publishing PDF documents on Web sites:
1. When including a PDF on a Web site, let users know that they will be downloading a PDF and the approximate file size.
2. On pages containing PDF files, place a link to the Acrobat Reader download page on Adobe's site.
3. Consider placing editing restrictions on your PDF files.
4. Remember that Google will include your PDF file in its index. If you don't want the files included, use suitable robot.txt files or HTML commands.
5. Using a resolution of 72dpi will greatly reduce the size of a PDF. Higher resolutions are only required if you need to include print-quality graphics (such as photographs).
Planet PDF (www.planetpdf.com) offers a huge range of tools, tutorials, links and other resources. It is independently run, so it gives users more choice of PDF tools than Adobe.
Adobe (www.adobe.com) is the king of PDF, but the Web site is a nightmare to use.
These sections will get you started:
Create PDFs online:
Acrobat Product Information: www.adobe.com/products/acrobat ePaper (home of the PDF): www.adobe.com/epaper Google (www.google.com) is a search engine that includes PDF files on Web sites.