Most colour documents are printed using the four-colour process, or CMRK. Graphics are broken up into percentages of cyan, magenta, yellow, and black inks, each printed in turn using a separate plate. These ‘separations’ can be generated by your DTP software, but your bureau or printer may use other means. PDF files can contain separations, but are more commonly created as composites, with the critical stage of separation left to the printer.