buyer wants signature comfirmation added. How do I charge her after item has been purchased

[caldreamer]

I don't think you can through EBAY after purchase was already paid for. Only thing I can think of it to ask them for send money directly to your PAY PAL account.

[nobody*s_perfect]

If the buyer hasn't paid yet, send her an invoice with an adjusted total cost. If she has paid, then send a money request from PayPal.  

To get their PayPal email address, go to the original payment transaction. You might have to click on the Issue refund link at the bottom of the payment details; this brings up a window that has their PayPal email (as well as a box where you can adjust the refund amount etc.).

Don't forget that PayPal is going to charge you 30 cents plus 2.9%, so you might want to bill them a nice round $3.00.