What color profile should I set my file in? RGB or CMYK? And what's the difference?
Please design your file to be in CMYK (Cyan/Magenta/Yellow/BlacK). Production presses such as the one we use use CMYK toner, and require the files to be in that format.
If you are sending a Word document which is not graphic intensive, you should not have to worry about this issue. We do convert RGB to CMYK for you if you send us the files. However, we recommend that you design before you submit, because some colors shift when they are converted. It is better that you see the shift before you send it in.
For most image editors, there is a setting either in the Save action, or the Image Setting action that can convert to CMYK.