A person can sign an instrument as an authorized agent of the drawer, but the instrument is not negotiable unless the drawer also signs it.

Negotiable

Refers to the quality of a document or instrument that allows it to be transferred or endorsed to another party, thus enabling the recipient to claim the rights specified in the document.

Authorized Agent

An individual or entity that has been given legal authorization to act on behalf of another person or entity in conducting business or legal affairs.

Drawer

The party that initiates a draft (writes a check, for example), thereby ordering the drawee to pay.