File Extensions PDF File Format SUMMARY: Explains what PDF files are and how they can be created or read.   The PDF, or Portable Document Format, is a file format created by Adobe Systems. This format represents a way to transmit brochures, booklets, tax forms, restaurant menus, software documentation, or virtually any other type of word processing or desktop publishing document. This file format is popular on most operating systems, allowing people to transmit all types of content without having to use a myriad of different file viewers. PDF files are usually created with Adobe Acrobat, though other freeware and shareware tools abound. They are normally viewed with Adobe Reader, a freeware application Adobe provides to help continue the use and adoption of PDF files. Windows users: NOTE that unless you have configured your computer with the file extension viewing tweak, it is possible that a filename that looks like it ends with ".pdf", especially one attached to an e-mail message, actually has a hidden OTHER extension, meaning that if you double-click the file, it may actually run a computer virus!   Add: Del.icio.us | Digg | Furl | My Yahoo!   Discuss This Tip Print This Tip Get E-Mail When New Tips are Online Return to the File Extensions page.