A system for printing documents 100 having a position identifying pattern 108 on them comprises a memory 403 arranged to have a document definition 410 stored therein which defines a document having at least one pattern area 107 and a printing control system 400, 408, 306, 307, 309 arranged to print a document instance from the definition by allocating an identity to the document instance, associating an area 700, 718, 720, 721, 722 of pattern space with the document instance, and printing the document instance, wherein the printing control system is arranged to move the boundaries of the defined pattern area before printing the document instance.