Thank you for your post.
Our Development and Testing departments are already aware of this issue. A blank portal (showing or sliding up) when saved to PDF will cause an error.
Another customer on the forum has also encountered this issue, and the workaround is to set a Hide object when condition on the portal. For more information, see:
I have attached your post to the original report. When more information becomes available, I will post again.
This issue has been addressed in FileMaker Pro 15.