When you create a project for printing, it’s recommended you change RGB to CMYK to avoid potential color accuracy issues. The vast majority of printers for both home and commercial use employ a different color model from electronic display devices such mobile device screens and computer monitors. 
Computer monitors use an RGB (red, green, black) color model, suited for getting a wide dynamic range of colors of a dark screen. In contrast printers tend to use CMYK (cyan, magenta, yellow, and “key color” black) since most paper and card stocks are light colored. Changing your color model to CMYK lets you get an approximation of the color of your final prints, making it possible to adjust your file before you have it printed. Please note that the color you see on your screen may be different depending on how your monitor is calibrated.
If you don’t change RGB to CMYK before you print, your printer will automatically make the switch. The problem with this automated change is that you will not get to see an approximation of the end product until you get your final print, which can lead to an unpleasant surprise. Color disparities can be especially obvious on large format materials such as posters. This can be important for businesses that use specific colors as part of their branding.
If your design app allows it, it’s best to start any print project in CMYK, so color shifts will be easier to deal with. Converting at the end of your project can result in dramatic changes that will take more time to fix. But in any case, it’s always best to set your file as CMYK before sending it in for printing.

Here’s how to change RGB to CMYK on Adobe Photoshop CS6, Adobe Illustrator CS6, Corel Draw, QuarkXpress 8, and Microsoft Office Publisher.

Learn more: How to Convert RGB to CMYK in Photoshop and Illustrator (With Screenshots)
Repeat steps 1-5 for objects with an outline.
Quark recommends exporting to PDF as the best way to change RGB to CMYK
“Press- High Quality/High Resolution” is a QuarkXpress preset for making print-ready files. Choosing that option does the following to your file:
All “PDF style” options in the “Export as PDF” dialog window can be adjusted.
Check out this article for a better understanding on the use of color:
Why You Need to Change RGB to CMYK for Print
Comment below to share additional tips and shortcuts on how to change RGB to CMYK for popular apps.