I already printed the label via PBS for the audio CD that I planned to mail later today.  Now the requestor has asked me to instead mail the CD directly to the person he is giving it to as a gift.  Am I allowed to cross off the address and write in a new one? 

Did you purchase PBS postage, or did you just print the label?

The requestor sent me a link for creating a custom label, but it says I have to rebuy the postage then.

Can the requestor now change the address and I can then just reprint it? 

Otherwise, I am just going to mail it as is.  I wish he had messaged me sooner!

AS posted on your thread in Questions forum, you should not alter the mailing address of a printed label.  Unless the sender wishes to cover your lost postage, I'll agree to may just wish to mail it to the original requester and let him be responsible for forwarding to his friend.

If it was a label without DC and/or printed postage, there could have been options.  But since the requester didn't properly use the 'mail to a different address' option, it is their error not yours.

In another thread, someone suggested that you *might* be able to get a postage refund (minus 10%) by taking the wrapper to the Post Office.  Still, I agree that this would be "above and beyond".

Postage printed from an online source must be refunded from that same online source.  The PO can not refund postage from PBS, Endicia, Click-N-Ship, etc.  The PO can only refund actual postage meter postage, not onliine postage.