[XeTeX] Outputing PDFs in CMYK ColorSpace

[George N. White III]

On Fri, Jan 15, 2010 at 10:17 AM, Clinton Gormley <clint at traveljury.com> wrote:
> Hi all
>
> I'm producing PDFs with xelatex destined to be printed in a newspaper.
> The printers require the PDFs to use a CMYK colorspace, but I can't find
> any option to set this.

You need provide more information about the document: do you have
external figures/graphics?   What colorspace do they use?  How is
color used in the document -- just a few specific colors or
many colors?

Is this a 1-shot project or something you will be doing many times?

> The only solution I've come across is the one mentioned in:
> http://newsgroups.derkeiler.com/Archive/Comp/comp.text.pdf/2006-03/msg00217.html
>
> $ pdftops -level1sep original.pdf separated.ps
> $ ps2pdf14 separated.ps

The CMYK conversion needs to be checked for your documents.  The OP
does mention
some of the quick checks the printer made using Adobe Acrobat that
found problems
with the color usage in the document.  Such checking is standard
practice, and you
should try to find a way to perform the checks yourself.

> Is this still the best solution?

Post-processing using commercial tools may give better CMYK results.
If you use external figures you may get better results converting them to CMYK
before processing with xelatex as the conversion can be tweaked for each image.

Many low-end tools do not convert RGB to CMYK reliably.  You may end up with
"black" that has CMYK with small CMY values or map a range of colors to the
same CMY values.  There are tools that help check color usage in a document --
many printers use them and will refuse to print a file that has
problems, but of
course it is better if you can provide a high-quality PDF from the start.

Many commercial printers are skeptical of software they haven't encountered
before, but are impressed with the quality of (la)tex layout and may be willing
to put extra effort into helping you getcolors right -- good products
help build
their business.

-- 
George N. White III <aa056 at chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia