Many, many thanks to all who helped me out with concrete offers and advises. Mostly to Peter, thanks.
The solution right now is: The printer transformed my PDF into a PostScript file and then he created a new PDF-file with Acrobat Distiller - after having done all this it works fine in this printing house. It is somehow strange and I couldn't get more informations from the printer which software he uses to expose the pages and so on .... So, for the moment my problem is solved - but in the end not really - we'll see next time ... Detlef
