Full colour printing – CMYK? RGB? Spot colours & pantones?
One of the most common reasons for artwork being rejected is because it (or components thereof) are set up in RGB. Experienced graphic designers may wish to stop reading here – this will be covering old ground for you (however you’re all guilty of this...How to tell how many printed pages (PP) are in your brochure
Page numbers are a constant source of confusion for less experienced graphic design customers.