digital file sales

Can anyone recommend an ecommerce plugin for selling pdf downloads onsite?

I’ve looked at several, wp simple paypal shopping cart is the only one that I can get to run, but I’m not sure of it’s suitablility for automated digital file sales.

I’ve also installed, tested and disabled wp paypal buttons, simple seller, and download per paypal, but run into bugs or simply couldn’t configure them thru lack of any meaningful interface/controls to do so.

I’ve also looked at such ones as wazala ecommerce store, and and ecwid shopping cart, but these seem for advertising for their own sites/ signups and services elsewhere before you can use them.

I just need something to post, say, a buy now or add to cart button where it’s wanted, pay thru paypal and automatically give access to the download link for the customer.

Any tips on what’s good?

Thanks, Bob.