Portable Document Format (or PDF) files are highly compressed page description files. They can contain text and graphics, and they can easily be scaled and displayed or printed. Unsurprisingly, PDF is like an improved version of PostScript, also from Adobe, that is tailored to electronic presentation of print documents.

• PDF is ideally suited for the electronic dissemination of print documents. It boast "the look and feel" of paper. Frequently, this make PDF files hard to read on screen.
• Like DVI files, PDF files are hard to decrypt and modify. This is good for electronic publishers who want to protect "definitive versions" of a document from being modified.
• Using Adobe software, PDF files can be created with about the same effort as printing. Thus it is easy to produce PDF versions of TeX documents. Again, using Adobe authoring tools, it is also realtively simple to add high quality color graphics to such documents.
• Searching PDF files requires special indexing and searching software which must be purchased from Adobe.
• PDF addresses the desire for author control over layout, in contrast to the original conception of HTML where the reader controlled many layout features.

  Consequently, PDF is limited to offering links for interfacing with other, more interactive web page elements.

PDF Readers

Like PostScript, PDF is a proprietary language. Adobe distributes a free viewer for PDF files, called Acrobat. It is available for most computer platforms, and is simple to install.

If you want to redistribute Acrobat from your site (as you probably would if you had many PDF documents online) you can do so after signing a licensing agreement.

Adobe is also releasing a new reader that runs as a Netscape plug-in. One of its main features is the ability to download PDF files a page at a time. This eliminates the experience of downloading a large, multi-page PDF file only to discover, after finally getting to see the first page, that you aren't interested after all.

Creating PDF files

Creating PDF files requires purchasing software from Adobe. At the time this page was originally written (1996), the main options were:

• Acrobat Writer -- a driver that allows you to "print" to PDF files from common business applications like word processors.
• Acrobat Exchange -- an authoring tool that allows you to put in navigations links, annotations, etc.
• Acrobat Catalog and Search -- tools for indexing and searching PDF files.
• Acrobat Distiller -- a PostScript to PDF converter.