PayPal does not handle the digital download side of things if that's what you're asking.
You can use the standard item button code however, the management of the download takes a bit of work on your end. You simply just can't return the customer to a URL without some sort of security management in place, else, the URL can be shared with anyone.
There's a few options for digital downloads ... if you're into programming your own stuff, then check out PayPal's Instant Payment Notification or IPN feature. IPN is a message service that notifies you of events related to PayPal transactions. You can use IPN messages to automate back-office and administrative functions, such as fulfilling orders, tracking customers, and providing status and other transaction-related information.
You can learn more here:
https://developer.paypal.com/webapps/developer/docs/classic/ipn/integration-guide/IPNIntro/
And here's a link to the User Guide:
https://www.paypalobjects.com/webstatic/en_US/developer/docs/pdf/ipnguide.pdf
More info:
https://developer.paypal.com/webapps/developer/docs/classic/products/instant-payment-notification/
If all of this is a bit more than what you want to get into, another option is go with a 3rd party service. They do most of the work for you. For example, check out this service:
http://www.e-junkie.com/
