If you go into the Transaction Details of the item on Paypal after logging into your account from a desktop computer, there should be a 'reprint label' at the bottom of the page someplace. But DO NOT delay. You have 24 hours from the time you bought that label to reprint it. You should also find a link in the email that paypal sent you after you purchased the label that allows you to reprint it.
If you have to void that label for whatever reason, you have only 48 hours to do so.
The clock is ticking.
Good luck.