If we print the label with postage and something happens that we can't ship the book, can we cancel the wrapper and have the postage refunded?

I couldn't find anything in the help/faqs about this.  I'm sure it's there, I just couldn't find it.

What if I print with postage and then can't send the book, or my printer malfunctions?

• If you cancel a transaction (or the system cancels the transaction if you did not mark the book mailed in time) after printing with postage, the postage can't be refunded by PBS.  The funds are transmitted to USPS when you download the wrapper with the postage on it.  You could try taking the printed, unused wrapper to the PO and discussing this with them.    We have no mechanism to recover these funds from USPS ourselves, but individuals may be able to do so.
• If you download a wrapper with postage and then your printer malfunctions, remember that you can reprint the wrapper (you can download it again) using the RePrint Wrapper button without being charged.  This can be done from any computer that has a working printer attached.   You should try this option if it is at all possible before cancelling--once canceled, the postage cannot be refunded.

It was under FAQs in printable postage.

Ann, if you can't send the book (it got damaged or you can't find it or whatever) you might want to ask the requestor if she wants a different book from you. You can use the wrapper to send that book instead.   It's a long shot, but it might save you wasting postage.

Internet postage will not be refunded to individuals by any USPS office. You'll be disappointed if you take it to a PO and ask them for a refund.

If you have a Paypal account, you might want to check out the Paypal mailing service to print postage paid labels. Ifor any reason you don't use the label  (or it prints wrong, etc.) you have 24 hours (or is it 48?) to void the label and get a reimbursement.

The payment for the postage comes out of your Paypal account, and always includes tracking/delivery confirmation. It can be used for media mail as well as the rest. There is no added on fees for the service.

The URL is: https://www.paypal.com/us/cgi-bin/webscr?cmd=_ship-now

It's not as convenient as using the PBS labels and, of course, you don't get a PBS "instant credit" but at least you will have confirmation of delivery is the person doesn't mark it received.