Additional Study Information: The purpose of this study is to determine the effectiveness of combining immune therapy, pembrolizumab, with a hypomethylating agent, azacitidine, for pancreatic cancer. People who have advanced pancreatic cancer with disease progression on first-line therapy are usually treated with a second chemotherapy regimen. However, there is no single accepted chemotherapy regimen and national guidelines recommend chemotherapy or clinical trial participation. In this study, all study subjects will receive a combination of immune therapy (every 3 weeks) and a hypomethylating agent (every 4 weeks).