A printing unit contains at least one printing group which is comprised of at least two cylinders which cooperate to form a printing nip. At least these two cylinders are interconnected in a positive fit by a drive. The two cylinders can be engaged with one another in a first position (ON), or disengaged from one another in a second position (OFF). The two cylinders can also be disengaged from each other at a spacing distance in a third position (STOP). That spacing distance is sufficient to allow a web in the printing operation to be guided between the two cylinders without making contact with the two cylinders.