PDF (acronym for Portable Document Format) is a popular graphic format due to its capability to integrate images, text and 2D graphics so that the generated files are small enough to be distributed across the Internet.
PDFs are frequently used for e-mail attachments or for shared files and are usually created from other files.
Most PDF makers function as a virtual printer for Windows, and users simply need to choose to print a file to PDF format (after they have previously installed an application that offers this function).