When you send a letter requesting a PFD do you just ask for their signature or does it need to be notorized? What if you pay but they don't delete it?
A documentation on the company's letterhead, signed by an authorized agent of the firm is all that is needed. Requesting a notorized document is pushing the "goodwill" factor over the edge, and most likely will backfire.
Not too mention that this tactic rarely works anymore in light of most agencies subscription "contract" with the credit reporting agencies. Try for deletion via the FCRA dispute process before resorting to this dubious mechanism.