PDF Product Vouchers

Customers often want to have a downloadable pdf voucher set to be delivered to the recipient on a particular date (Christmas, birthday, etc), rather than when an order is marked as Completed. That is, I want to be able to mark an order as complete, receive payment, and forget about it, but have the pdf voucher delivered to the recipient automatically on a date selected by the purchaser at the time of ordering. At the moment, having a recipient email is not optimal because the purchaser doesn’t want the gift sent upon payment but rather on a specific date.