How would one automatically send a link to a user that has paid for a downloadable merchandise. For this example, let's say an e-book. The user pays for an e-book and a link is automatically generated for them to download it. I will of course have the e-book file on the server. However, users should not have access to that file by just typing in the link in the browser. So does one implement this?
I also added more points to the question for suggestions for 3rd party software. So if you can recommend some software to use, that will help as well. This is so that I have the option of creating it myself, or buying it.