How good is Word's password protection? [closed]

Judging from the results of a search for "break microsoft word password", it is not so secure. If you really need to keep it secret, then encrypt the file.

You could use 7z to compress and encrypt the file. It uses AES-256 which is the same encryption standard used by the US government.

Another option is to use an email service that offers PKI secured e-mail. You and your recipient would both need accounts.

It's not good, unless you're on the latest office release (Office 2007 or newer)

I suggest you look at GNU Privacy Guard / Gpg4Win or if you're storing the data on a usb flash drive check out TrueCrypt

If you don't trust Word, you could create an encrypted file container using TrueCrypt. There's a good tutorial which explains how to do this.