This was just hashed over on the Framer's mailing list, although the issue was an incorrect character showing up in the PDF instead of Symbol, and the thread produced a couple things to check, including:
1. Make sure you have the Windows Symbol font installed.
2. In FrameMaker, check that your Symbol character tag uses the Windows "Symbol" font and NOT the "Symbol Std" font. Symbol Std is a private font installed by FrameMaker.