I'd like to offer a digital download in return for payment. The idea is that after completing the paypal process, they get returned to my website and can then download the file. But what happens if they make the payment and then can't download the file, for whatever reason?
Is it possible for them to get a transaction id from paypal, which I can then check somehow? Then if I can verify that they have paid, I can send them a link or email them the file or whatever, to resolve the problem. Is there such a way to verify that somebody emailing them has actually completed a transaction?
Does the seller see who has paid them, and if so how much do they see? (Assume in this case there's no need for the buyer to enter a shipping address, or anything else really)
When your buyer sends you a payment they get a transaction ID however this transaction ID generally will differ from yours as it is there individual transaction ID for sending the payment. You will also get a transaction ID for receiving the payment.
You will however be able to view their email address in the transaction details page. If there is an issue you could ask for their email address and search for it on your own account which will then bring up the transaction.