People, rightfully, worried about badness in CIA released PDFs might want to look at Qubes OS.

Qubes is a high security Linux distribution that takes sand-boxing to a whole new level. It puts a sandbox in a bunker and it will burn the whole thing to the ground when you are done. It can also route ALL your external network traffic through TOR if that makes you feel good.

It is all open source and free. I admit, I am having some difficulty getting it to install properly but it is in rapid development and not all weirdness has been vanquished.