Once Bullzip is installed, open any PDF and then choose Print and you'll find Bullzip at the top of the list of Printers. It will print to bullzip and then open the pdf on the screen, click the Security Tab and its got a place for 2 passwords (Im not sure why it has 2, I put the same PW in both boxes) then Save, it will open your saved pw protected file file and make you enter the password (I do this to make sure it opens for me) then attach that saved PDF to an email.

It doesnt zip the file at all, just adds a pw to the newly saved pdf.