Thanks once again for clarification Minimiro!

But what if I send the enclosed file (the PDF above) to the printers?
Will THEY be able to open it as 2 colors or not?

I mean, is this only a Photoshop-thingie and the printers will do it totally different or will they have "just" a CMYK-file too ??

btw: I sent the PDF to the printers, asking just that, but have not gotten an answer yet.
Commercial companies ALWAYS act way slower than the Talkgraphics-community ;-)

Wolfgang