The file format created by Adobe Systems Acrobat to represent documents that is not dependent on the original application software, hardware, and operating system which created them. A PDF file can describe documents containing any combination of text, graphics, and images in a device and resolution independent format. PDF documents can be a single page or many hundreds of pages and can contain hyperlinks. The availability of free reading software makes this an attractive format for publishing information on the Internet. PDF files are also used for exchange of information when the format is important (e.g. legal or historical documents). They are now also the preferred method of supplying data to commercial printing houses. A PDF file can be produced from a PostScript file using Acrobat Distiller. Many word processing and DTP applications can also produce PDF files directly.

http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/pdf_reference_1-7.pdf The PDF reference manual (version 1.7)