Use GPG (GNU Privacy Guard). It's essentially PGP, but free. It uses assymetric encryption (Public and Private keys) up to 4096 bits of keylength, which is sufficient for most people. There are graphical frontends for Windows available, such as GPGee (shell extension).

If you encrypt a document using a customer's and your own public keys, only you and your customer can open it. It is extremely difficult (if not impossible) for other customers to open your documents. There's even support for digital signatures.

Indeed, the casting is done.

No trolling, just have a laugh.

I'd mod you +50 Funny if that was possible.

Made my day!