Pathfinder is released under an open game license so that makes it completely legal to repackage and edit their content and release it. A project called d20pfsrd has done just this. These documents are the text only with relevant charts reworked. The artwork is all copyrighted by various artists and presumably pizzo. These documents are free to download not not illegal in anyway. They include the full text of the rules for the game and can be used as a great reference on a computer when your planing or playing games.
The first is the core book
This is the monster guide
If you want a dynamic reference the site http://www.d20pfsrd.com/ has a wiki of all the rules and content in a very easy to use format.