Signing on Someone's Behalf

This is the normal practice I have seen for signing on someone's behalf:
Type their usual signature line, sign your name above it and handwrite ‘for’ beside their typewritten name. It is also acceptable to use per or p.p.
Some Things to Consider:

• Have you been given authority to sign on their behalf?
• Does your company have a policy on what style they want used for signing for someone else?