gs -o cmyk-doc.pdf \ -sDEVICE=pdfwrite \ -dOverrideICC=true \ -sDefaultCMYKProfile=/path/to/mycmykprofile.icc \ -sOutputICCProfile=/path/to/mydeviceprofile.icc \ -dRenderIntent=3 \ -dDeviceGrayToK=true \ input-doc.pdf