I learned that you can sign something even if somebody else's name is on it

I ran into a problem. I needed to send out a letter, but my name wasn't in the signature block. I was told that I can simply write "pp" before my signature.

From Wikipedia:

"Also rendered per procurationem. Used to indicate that a person is signing a document on behalf of another person. Correctly placed before the name of the person signing, but often placed before the name of the person on whose behalf the document is signed, sometimes through incorrect translation of the alternative abbreviation per pro. as "for and on behalf of"."