To shorten a preparing time in an offset rotary press and to reduce a spoilage occurring during a series of operations.

A method for operating a printer comprises the steps of reducing (step B) ink printing of an ink roller group in decelerating (step A) from a producing speed, replacing (step L) a winding roll, and cleaning (step Q) a blanket cylinder. The method further comprises the steps of then independently controlling each printing unit to replace a press plate in parallel (step C), and signaturing (step D) a folding unit in parallel with replacing of the plate. The method also comprises a step of imparting a tension to a web (step F) by independently controlling the roller for guiding the web after the plate is replaced. The method also comprises a step of presetting the printer in response to next time printing conditions during its period (step E). The method also comprises the steps of then removing (step M) a cleaning liquid from the blanket cylinder at a high speed rotation of each printing unit in parallel with overheating of a drier (step H), preliminarily supplying an ink to the ink roller group (step G), regulating a color tone and a register (step J) and then accelerating stepwise from the regulating speed to the producing speed (step K).