how can I password protect (and encrypt) a pdf file that I received from someone else? For example, I may get a copy of my tax return from my accountant that I don't want anyone else to see on my computer or when I back up contents of my computer online.
I have only Adobe Reader 8 installed on my computer. So I am not writing these pdf files myself - I realize that then I would have full control over the security settings.
Microsoft Word and Excel files I can password protect. How can I do this for "received pdf files"?