The phrase "to print a proof" means to create a physical copy of something that can be reviewed and checked for errors or mistakes before it is finalized. Full definition
You can even print your proof of insurance or download it to your phone in most states. (progressive.com)
If you have made significant changes to the cover file, you might even want to order a new print proof copy before making the title available again. (selfpublishingrelief.com)
Select the «Print Proof of Payment letter» link under the «What would you like to do next» section and print the letter. (public.websteronline.com)