PDs provide a general (and sometimes out of date) description of what the job entails and are used to establish jobs and hire this most qualified individual rather than that lesser qualified individual. Note that they state "and all duties as assigned." Performance Plans are more specific as to what should be accomplished in a specific performance year and change at leadership's will; sometimes in response to employee suggesiton. It is understood that not all duties will be listed on a PD. After all, someone had to lead the Combined Federal Campaign, Plan the holiday party, etc. The remedy is for the superivsor to say "Do it."