What does PAC stand for after a doctors name?

The C stands for certified. However, PA's are not actually doctors. They are Physicians Assistants. No need for concern though. It's been my experience that PA's are not doctors only in a literal sense. One of the main differences between PA education and physician education is not the core content of the curriculum, but the amount of time spent in formal education. In addition to time in school, physicians are required to do an internship, and the majority also complete a residency in a specialty following that. PA's do not have to undertake an internship or residency.