will try to keep it simple
The only violation that occurred was the sale itself for profit.
The seller was entitled to download and print the document.
Therefore, however unethical it may seem, you are obliged to return it if he refunds.

Ed is the only one who can take the matter further if he chooses. As he had no contract with the seller any action by him is totally unrelated to your transaction. Ed has a claim because his work is being sold on ebay, not because you purchased it.

As I said in my email, first priority on principle is get the $$ back while you can.