PDF

The PDF is a document type created by Adobe that allows text and graphics to be displayed and printed in exactly the same way on any computer.

Adobe offer a free program called Adobe Reader that can view PDF on PCs, Macs and Linux computers. Macs also come with a built-in program called Preview that opens PDFs (so no additional software is required) and Linux distributions often come with open source PDF viewing programs (such as Okular or Evince).