Good plugin for "private" paypal transactions

I am looking for some type of plugin or trick that will help customers on my website privately pay for their products (which are personally uploaded by me) via paypal or some other form of payment without having it publicly displayed on the site for everyone else to see.

For example, some way I can give customers either a password or a url link via email for them to access and pay for their “personal” documents. Rather than have them displayed for some random person to buy on the site (which is very unlikely, but possible) I hope I am making sense here, thanks!