Well theres not much pending people can do at that point... beyond "you need to wait XX hours before you may try again." But that screen will already tell them that.

Not sure if sending them a message would be prudent, as theres Lots of pendings for a variety of reasons. If they didn't complete the transaction, they need to wait for the status to clear and try again. They cannot just go pay, as there will be nothing for it to match up to.

The common reasons for pendings:
- Someone gets to paypal and for whatever reason closes the window or goes elsewhere during the transaction
- Sometimes, depending on how they are paying (certain credit cards) require them to verify information further (ie wait for their credit card or bank statment to come and verify transaction numbers on it) before they will be able to proceed with the transaction.
- Someone clicked in to view a subscription option and used their back button instead of the cancel button.
- They are pending between the point that they signup from your site and the time the ipn hits your site with confirmation of payment. Under normal circumstances this should only be a few minutes.

In those cases the instructions on that pending screen should be sufficient. I recommend setting pendings to be deleted after an hour. That's plenty of time to distinguis between someone who just looked at the screen and a real transaction, and if they need paypal verification etc... that'll usually take a couple of days anyway. But there's no way to continue a pending transaction.

If you're charging for access to something, they won't have access to anything in the pending state