Due to time constraints bosses will sometimes ask staff to sign business letters on their behalf. In this case the proxy, or staff member signing on behalf of the boss, should sign her own name with the letters "p.p." before the signature. The name of the boss should be typed out under the signature.
How to Use "Per Procurationem"
The letters "p.p." stand for "per procurationem" which means "through the agency of." The person who does the actual signing puts these letters before her signature to bring attention to the fact that the sender of the letter is not the person who has done the actual signing. In the event a staff member drafts a letter, there is no need to reference this in the body of the letter as long as the boss, who is taking responsibility for the letter, signs it himself and is named as the sender.