You could use a compression utility and password protect it. WinZip has AES. WinRar has encryption. ALZip has AES and some others.
Password protected encryption does about the same job, but is easier to deal with. Talk to people about encryption software and their eyes will simply glaze over. "You send me your public certificate and I send you my public certificate, and you then..." At that point people are just lost. Symmetric non-public key encryption like you get in compression utilities is far simpler. "I send you the file, then you use the password to open it." People understand passwords.
However DO NOT use ZIP 2.0 encryption. It is weak. If you have a file in the archive that is known, then decrypting everything else is almost trivial. This is a flaw in ZIP 2.0 encryption and it is serious. If you KNOW that nobody has any of the files in the archive, then it's safe.
AES or ARIA are excellent.