Great question! I don't have much experience with physician assistant careers, but I found some information for you that might be helpful.
Visit www.aapa.org for some basic information about becoming a physician assistant. The best information I could find about the continuing education was at http://www.aapa.org/cme/requirements.aspx and http://www.nccpa.net/ContinuingMedicalEducation.
Lots of times hospitals will host conferences or seminars and PAs and other medical professionals will log hours by attending.