A printing press for security printing has an Orloff offset printing unit comprising a plurality of stencil cylinders which can be inked, in each case, by an associated inking unit, an ink-collecting cylinder which interacts with the plurality of stencil cylinders, an Orloff plate cylinder which interacts with the ink-collecting cylinder, a transfer cylinder which interacts with the Orloff plate cylinder, and an impression cylinder which forms a printing point with the transfer cylinder. At least the transfer cylinder which interacts with the Orloff plate cylinder in the thrown-on position is included by a first printing unit section and is mounted in or on a first part frame. The ink-collecting cylinder is included by a second printing unit section and is mounted in or on a second part frame which is different from the first part frame. The first and the second part frame can be moved optionally into a first relative position with respect to one another, which forms a working position, and into a second relative position with respect to one another which forms a maintenance position. In the maintenance position, a space is formed between the first and the second printing unit section and/or between the first and the second part frame, which space ensures direct access at least to the ink-collecting cylinder, to the Orloff plate cylinder and to the transfer cylinder which interacts with the Orloff plate cylinder. Moreover, the invention relates to a method for changing a printing forme and for starting production.