Exported PDF is presenting with a blacked out section on one floor plan only. The blacked out section does not correspond with any elements in the sketchup or layout files, nor does it correspond with the size of the view port.
Problem solved. It turned out to be a viewport that was focused on “nothing” in the sketchup file. I.e. a scene that had had the content deleted. The view port was overlaying another viewport. It shows up as clear square with no border in layout and a black square when exported to PDF.