Automatic delivery of file following payment

I sell a pdf version of a book (roughly 8 megs in size) from my website and for years have filled orders manually. I currently accept only Paypal payments, but may accept other credit card payments in the future. I'm looking for a way to automate the process. The minimum requirement would be this: A cusomter uses Paypal to order the pdf file, and within a short time they receive a link which he or she can use to download the book. Greater consideration will be given to a coder who can provide the following: A method to prevent one purchaser from sharing the download link with others who then download copies for free. I'm very flexible as to the approach, so long as I can obtain the desired results: automatic delivery of the file upon purchase, preferrably with safeguards against sharing download information with non-purchasers. Feel free to contact me with any questions or suggestions. Thank you in advance for your bid. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform MySQL available from host, if necessary