Hi, at the moment ghostscript(-apfl) and imagemagick have some problem with CMYK pdfs (for details see the link) which only occurs on 64bit platforms. There is a small patch posted on the url above which solves the problem, would be nice if it can be integrated to the ebuild.
Created attachment 64750 [details, diff] patch taken from upstream bugzilla
i included the improved patch (see upstream bug) in -r10