There have been several issues reported concerning printing/plotting to PDF. There appears to be an issue that the R&D team is working on. If you are experiencing this problem, can you please provide the drawing that your are trying to print and information about the settings and PDF writer that you are using. This will help us to better troubleshoot and fix the issue.
In the meantime, you can also try using the Microsoft Print to PDF selection.. It appears to be working well from our tests. See attached image.