I've got a useful business document that I think others would be interested in. It describes how to do something and provides data and text that people might want to copy and use themselves.
Are there any services out there that will let me do this and manage the downloads, licenses etc.
You could probably build your own system to do this (just grab the POST variables from PayPal IPN response and send off emails, validate codes, etc...), but if you want to check us out, email me at contact at bitbuffet.com and I'd be happy to extend your trial for however long you like (the default is 7 days). Offer applies to any interested HN'ers of course!