Thanks for the review @dtlegal!
I’ve wondered about that too, but you’re the first to actually mention it (so thanks, otherwise I wouldn’t know if it’s just a crazy idea of mine or something that will actually be useful.)
I’ve worked on payment stuff before but know it quickly explodes into a lot of work (for starters PayPal stops working randomly almost once a month and never admits to it!)
So I would think it would be best to let another plugin handle payment processing. Is there a payment processsing plugin you would prefer Print My Blog could with with? (Big names are WooCommerce and Easy Digital Downloads but they’re hardly the only ones.)