Converting PDF from RGB to CMYK with freeware or OSS
I print marketing regularly at my job, and everything is sent to us as PDFs. The problem is, the color profile is always set to RGB, and the resulting prints look terrible and don't match the colors of prints sent to us. If I convert the PDF to CMYK, it prints perfectly. The problem is, I can't use Photoshop at work (they won't pay for a license for somene in my position).
Can anyone recommend a free or open-source application that will allow me to convert RGB to CMYK in a PDF?
The already mentioned ghostscript is the free standard tool for this problem. If the use of the command line looks too daunting, you could use a free web service like: http://www.pdf2cmyk.com. You won't have any control whats really happening with your images, but the results are good as far as I tested. You can choose different output profiles (SWOP and ISO).
Use ghostscript, its the most obvious OSS tool for the job. Here's a sample for windows usage from stackoverflow :
gswin32.exe ^ -o -o c:/path/to/output-cmyk.pdf ^ -sDEVICE=pdfwrite ^ -dUseCIEColor ^ -sProcessColorModel=DeviceCMYK ^ -sColorConversionStrategy=CMYK ^ -sColorConversionStrategyForImages=CMYK ^ input-rgb.pdf
Tested and worked fine for 3 of my test PDF's. There are other ways to do color conversion to be more specifically what you want but this is probably enough for you, as for software selection.
Ghostscript is a quite complex application capable of very many things provided that you do the proper research. So it can do other things like add watermarks, translate pages etc. You probably need
-sOutputICCProle = my device prole.icc.
Script (or some other means) to convert RGB to CMYK in PDF?, 2012. Stackoverflow.