-> Using WinRAR software you can encrypt and set password for files..
-> you can download WInRAR from this following link..
-> reduce the file size
-> Encrypt the file
-> Set password
-> easy to use..
Steps to follow:
Launch the latest version of the WinRAR application (link in Resources) and click "Tools" from the menu bar.
Click "Convert Archives" from the list of options and then click the "Add..." button.
Select the archive that you want to encrypt and then click "OK."
Click the "Compression" button and then click the "General" tab.
Click the "Set password..." button and then type a password in the "Enter password" input box.
Reenter the password in the verification input box and then click the check box next to "Encrypt file names."
Click the "OK" button and then click "OK" again.
Click "Yes" when prompted if you want to encrypt the converted archive.
Click "OK" to convert and encrypt the archive. Click the "Close" button once the encryption is complete.