PTO

PTO is an abbreviation for:

United States Patent and Trademark Office or any other Patent and Trademark Office
Power take-off
Pacific Theater of Operations - World War II
The inscription "Please Turn Over!" at the bottom of a sheet of paper
"P:T:O:", a music track on the Klaus Schulze album Body Love (1977)
Paid Time Off - used as an abbreviation for holidays in USA
Parent-Teacher Organization, a decision-making body at many schools.