Portable Document Format (PDF)
PDF is a graphically oriented file format designed for electronic interchange; it was developed by Adobe Systems Inc. for use with its Acrobat software. In a PDF file, any page in a publication can be displayed or printed by a user in a form virtually identical to the page that appeared in the publication (including richly formatted text, graphics, and colors).
Adobe has released a free Acrobat reader for PDF files. With the Acrobat reader, a user can view and print PDF files; in addition, a user can extract text into ASCII or Rich Text Format (a file format that preserves some of the font and formatting characteristics of a document) and perform searches on the document.
Download the free viewer for PDF files available from Adobe Systems.
The usual protocol is to left click to view the document, or right click to download it to your computer.