Pantone Matching System or PMS, is a system that uses premixed inks in offset printing. When you are printing letterhead, envelopes or business cards it was typical to use a PMS ink to achieve consistency in your ink color on all elements. With businesses looking to save money, many have opted to print digitally.
How do you assure that your logo color stays consistent? Simple, make sure the CMYK build is the same in all your files. Otherwise, your blue PMS 286 might look purple. This is extremely important when you are using your brand color as an accent color in your document.
If it is critical that your brand color remain precise throughout the run consider printing 4 color process + a spot color, with that spot color being your PMS ink. This is the only way to assure that from page to page your brand color will remain true.