PDF (Portable Document Format) - 

• A file format developed by Adobe Systems as a means of distributing compact, platform-independent documents.
• PDF documents are superficially similar to HTML;
  • a PDF document may contain images and text, as well as hyperlinks
  • However, as PDF is based on a variant of PostScript, each document is completely self-contained--packing text, graphics, and fonts into a single file.
  • Because PDF documents are World Wide Web accessible--yet display and print exactly as intended--print publishers often favor PDF over HTML.
• PDF files can be viewed with the Adobe Acrobat Reader or the Acrobat Reader Web-browser Plug-in, both of which can be downloaded for free from Adobe.
• PDF files can be created with the full version of Adobe Acrobat.