How to create download link after paypal payment by user

Hi

How to create a secure download link and thank you page with the help of wp simple shopping cart page. I have seen the tips and trick video but there is no mention of download link (there is documentation only for creating the shopping cart) But what about letting the user download the product like pdf, zip, rar etc after the user has made a payment through paypal and returned to the Thank you page.

Please help.

Thanks