Screen Colours
When viewing the colours in your job on-screen, you are looking at colour which is made up of red, green and blue light, and these colours cannot be exactly replicated with ink on paper. How colours appear on-screen will also vary depending on how your monitor is calibrated. So please always choose your colours from a Pantone book for a predictable result.
The colours in your PDF will also vary depending on which simulation profile you are using to view it in Acrobat.