PublishCMYK is a tool to convert RGB Pictures to CMYK.
Including all formats of convert (pdf,jpeg,jpg,tiff,gif). You can use ICC/ICM Profiles to proof the colors.
This is important for Industrial printing.
If your source picture is in RGB, your source ICC must be a RGB profile. If you want that your resulting image is in CMYK your destination ICC must be in CMYK.
Pdf is not working perfect vor all OS.