I want to print a map I made with qgis. For the print I need CMYK-colors but the print-composers pdf-output is RGB. How can I convert the RGB-map/-pdf to CMYK?
I highly recommend ghostscript - it's available for free both on Linux and Windows. See https://stackoverflow.com/questions/3418268/script-or-some-other-means-to-convert-rgb-to-cmyk-in-pdf for the solution.