I found a free tool called BoncleExpress at http://www.boncle.com and it allows file encryption for my private documents. I can specify the recipients, so only the recipients in the list can open my file.

For encryption, I attach my documents, enter the recipient's email and save it as a secure package. Then I use my email client to send it out.

For decryption, the recipients need this tool to decrypte my secure package without entering any password. Usually, PGP requires password to open the file.

Does any one have used this tool? This tool seems interesting, but I wonder why the recipients do not need to enter any password to open my package?