Problem with Printing to PDF in WP 2021

I published a file to PDF (commercial printing) in WP2021. It showed up alright in Adobe Acrobat. When I uploaded this PDF to a company to be printed, their program could not work with it because it had an error in it. I repeated the procedure from scratch several times, always with the same result, but once also Acrobat said there was a fault in it. However, when I thereafter did the same thing with the same (unaltered) WP document in WP X8, the PDF was accepted as faultless.