mono= 1, XpdfPrint generates monochrome output, even if the printer appears to be color.
This setting is only relevant for GDI printing, i.e., for
non-PostScript printers, or if
pdfPrintForceGDI is in effect. It
is ignored when XpdfPrint generates PostScript code.
pdfPrintResetParams resets this to its default value of 0, which
means to generate monochrome output for monochrome printers and color
output for color printers.