Adobe's Acrobat is a file format for exchanging set documents on the web. This file format captures all text, graphic and formatting features and creates a single small file which can be accessed by almost all systems.

The Acrobat Reader allows you to view and print these files, and is available free from Adobe.

Most recent browsers come with Acrobat built in, so the file will open automatically.
But if you require the Acrobat Reader it is available from Adobe's website free of charge.
Simply follow this link and follow the instructions.