Abstract: Embodiments herein include a method of identifying sheets within a stack of printed sheets for sorting or further evaluation. In one embodiment the method comprises printing non-test production printing job(s) on sheets of media and outputting the printed sheets into a stack of sheets. The method monitors the printing of the non-test production printing jobs and, upon the occurrence of a “predetermined event” during the monitoring, adds a unique marking at an edge region of a printed sheet (of the non-test production printing jobs) being printed to create an identifier sheet from one of the sheets of the non-test production printing jobs. The unique marking is visible from the side of the stack of sheets. The identifier sheet is then output to the stack of sheets with the other sheets of the non-test production print job. During the remainder of the printing of the non-test production print job the method continues the printing of the sheets and the monitoring.