on 30-11-2013 09:59 AM
on 30-11-2013 12:03 PM
on 30-11-2013 01:58 PM
on 30-11-2013 02:06 PM
If you are able to issue a refund for the original payment, you can resend an invoice with postage included, however it could drag out the process for the buyer as a refunded eCheque when repayment is required can be a major PITA for the buyer.
The other option is to generate a separate invoice from PayPal for the postage amount only. That will allow things to be processed faster, but not necessarily the ideal way from the buyer's perspective (it is advisable for buyers to make a single payment for the item with an invoice that reflects the goods are being posted).