Ability to add a watermark in proof

[#1]

Description - We would love the ability to add a watermark to a proof from the proof creation screen

Why is this feature important to you - we want the ability to mark proofs as such to prevent confusion on what is a proof and what is a final product

How would you like the feature to work - on the proof creation screen we would like a checkbox for "add watermark to proof"

Current Behaviour - Proofs are created, no watermark exists.