PDF is an Acronym and FileExtension for Portable Document Format.
What is PDF
PDF is a format specified by Adobe which describes how to embed a multitude of resources in a single file, and also defines and describes formats for these resources, primarily PostScript with extension functions to enable the features PDF delivers beyond PostScript. Essentially, it is not a descendant of PostScript so much as an advanced container format for PostScript documents.
PostScript (and the Type1 font format, for that matter) are, of course, also Adobe brainchildren.
Why use PDF
PDF is the format of choice for distributing documents because:
- They can't be trivially changed by the receiver. (MicrosoftWord documents can be.)
- It is a true page description language. The same document will display identically on any viewer. (MicrosoftWord documents are notorious for displaying differently on different machines, depending on the version of MicrosoftWord in use, the fonts available to the machine, and the type of printer that computer is using as the default printer.)
- The format is described by an unencumbered, published standard. (Microsoft have been known to change the undocumented Word document format to force users to upgrade.)
- Because it is an open standard, viewers are available for many platforms (and can be written or ported to those without one). This means people can read the pdf file you send, even if they don't use the same software or OS.
- PDF files do not include macro code, and so can not carry viruses or malware in the way that MicrosoftWord can. However a specially created PDF can cause problems such as buffer overflow attacks to infect a system with malware. This is generally limited to one particular version of a reader and not all products.
Viewers for PDF
- AcrobatReader: by Adobe, ClosedSource, available for all major platforms.
- GhostView: Free, available for all major platforms. In KDE and GNOME, there are wrappers to better integrate it with the DesktopEnvironment: kghostview and gnome-gv, respectively.
- xpdf(1): Free, runs anywhere an X11 server is available. It tends to do a better job than GhostView. There is a GNOME version called gpdf, which based on the original xpdf code but has "better desktop integration".
- Evince: a Free multi-format viewer for GNOME 2.9 or later. PDF support is based on the xpdf(1) code, navigation is supposedly better than gpdf, and hopefully will be better maintained (gpdf development seems to have slowed or stopped).
Creating PDF documents
The obvious way is Adobe's commercial AdobeAcrobat, and if you're a professional and need all of the advanced features of PDF, that is your best bet. If you are less ambitious, there are many other, completely sufficient options available; see our CreatingPDFs page.