Print another annual receipt marked as duplicate

[tpokorra]

By law, we are only allowed to print a receipt once.
But if the donor tells us he lost his receipt, we can send another copy, and write DUPLICATE on top.
Should we store which receipts we have already sent, and automatically insert DUPLICATE on the page?

Another way: we only send digital version of the receipt as PDF, without a signature, and we can send that multiple times.