Have you tried just opening the PDF in Word 2013 to see how it would handle it?
As for the error message, that's likely a survival of an old bug. It helps to delete unnecessary section breaks, but the main thing to do is to open the
Columns dialog and select the preset picture for One, which checks the "Equal column width" box. If you have multi-column sections, you may have to set them to a single column temporarily to get rid of the problem.