We currently use a module to distribute serial codes to customers who buy downloadable software from our website, macgames.co.uk. The change we require is for a download link for the purchased software to be included in each serial code email. The download link would obviously be different for each of the 50 or so products we offer.
Prestashop currently sends a generic order confirmation email, so if it is easier, you could write a new module that sends a different automatic email depending on which product or products have been ordered (that would contain the download URL). That is essentially what we require, but combining it with the serial code email would just streamline our sales operation, if you're up to the challenge!
I know this sounds slightly confusing, so please don't hesitate to get in touch to clarify anything!