I recently learned of a great add-on for Google Forms while listening to The House of #EdTech podcast.
Certify’em allows a Form creator to automatically issue out certificates to those who complete a quiz, test, or assessment created in Forms. This add-on is currently free and offers up several free templates to use for your certificates. You also can easily create your own following the instructions found here: Custom Templates for Certify’em
You can check out an example that I created here: Certify’em Test Example.