PDF conversion prints only in blue

Hello,

I converted an azw file to PDF, conversion is ok, when I open the file, but when I want to print, the black letters print in cyan (blue).
But on screen all letters show in black.
I tried a different PDF files, they all print normal in black.
What could have gone wrong and how could I change it?
Simple would be to print B/W only, but there are color graphs in there as well.

Thanks