Download Purchase Tracking

Hello,
I’m hoping to sell a book that can also be downloaded as a PDF, purchased using PayPal. I know there are lots of PayPal plugins, but I’d really like to find the right one instead of going through all the trial and error.
WHAT I REALLY NEED is for the plugin to be able to give the book for free to a list of emails, and that each email could only download it for free once. It’s a promotional thing I’m offering to people who may be carrying my book in their stores.
If anyone knows of something like this, I would really appreciate the help. So, THANKS EVERYONE for all sorting through the mass amounts of plugins out there and finding out what really works.
Cheers!