How to protect documents on your computer from people stealing or seeing them?

I am not a Mac user therefore I'm not very fluent with apple software, but I am sure there is a encryption software available for you. By encrypting your file you are essentially changing the text to nonsense such as "u2u?9(8&" which no one can crack without a password. This might work but I cannot recommend it since I haven't used this one: http://www.net-security.org/article.php?id=1283. I hope this helps!