This is a patch to resolve a long-standing issue with CMYK color spaces. DeviceCMYK is a device-dependent color space and so should always be associated with an ICC color profile. In Acrobat the default profile is "U.S. Web Coated (SWOP) v2", which unfortunately is only available from Adobe under a non-free license.
I've modified PDDeviceCMYK to use an ICC color profile rather than a hardcoded transform, this allows the user to use their own profile. I've included "ISO Coated v2 300% (basICColor)" as the default profile, which is from OpenICC http://www.freedesktop.org/wiki/OpenIcc/ProfilePackages/ redistributed under the zlib license. This color space is an open alternative to a version produced by ECI which is highly recommended as a generic CMYK profile.
Note: Using ICC profiles is a huge improvement on the matrix-based transform used by Xpdf, Poppler, MuPDF, etc.
This patch requires the following file to be deleted: