Public accountant.
Power amplifier.
Public Act.
Pennsylvania, a state of the United States of America
Papua, a province of Indonesia
Pará, a state of Brazil
Palestinian Authority
Proto-Algic (sometimes abbreviated PAc to distinguish it from Proto-Algonquian)
Proto-Athapaskan
Proto-Algonquian (sometimes abbreviated PAn to distinguish it from Proto-Algic, but usually just abbreviated PA with Proto-Algic being abbreviated PAc)
Someone whose job is to assist and organize someone else's day-to-day business or personal tasks.