What is a PDF?
Internet Marketing Dictionary | PDF - Portable Document Format

A PDF file is a file that typically exists in a format that cannot be changed and yet is readable by most people.

PDF stands for Portable Document Format and the format was created by Adobe Systems in around 1993.

The advantage of PDFs is that you can be sure that if you send someone a PDF they will view it as you intend: the fonts will be what you specify, the font sizes will be as specified. Any images will appear in the right place and so on, yet the reader will not readily be able to edit the document. In fact you can put password controls onto PDF documents too to stop unauthorised people reading them.

Internet Marketers like using PDFs as free reports because they have a higher perceived value than a web page yet they can include links to websites in the text. This means that a marketer can create a free report about something and in that report refer to a product that he is an affiliate of. He can do this in such a way that when the reader clicks on the link in the report to find out more about the product, they go via the report creators affiliate link. Any subsequent sale that arises generates a commission for the writer.