Hi Li,
Are you getting the same error that Charles was getting, or a different one? I know you're in the same office.
Have you confirmed that you have a PDF viewer installed?
Other solutions would be:
1. Check the plotter driver being used in the Publish command. You should set the publish to PDF, and the PDF Preset ideally to DWG to PDF.
2. Try one of our recommended 3rd party PDF plotters for better publishing systems. I've tried Acroplot with this with good success.
Let me know the results from troubleshooting those.
-Amanda