Printing machine with modular additional printing group

There is described a web-fed or sheet-fed printing machine for security papers, in particular banknotes, comprising a machine frame (100) in which is located a main printing group (10, 13, 15, 20, 23, 25), the printing machine further comprising an additional printing group (1, 2, 8; 1, 2', 8; 1 ,2", 8), independent of the main printing group, placed upstream of the main printing group with respect to a direction of displacement of the web or sheets for performing additional printing of the security papers prior to printing by said main printing group. The additional printing group comprises an inking module (1) containing at least one inking device (3), and a printing module (2; 2'; 2") comprising a cylinder arrangement including a plurality of cylinders (4, 5; 4', 5', 6', 7'; 4", 5", 6", 7"), the printing module being interposed between the inking module and the machine frame of the printing machine. The additional printing group is constructed in such a manner that the printing module can be decoupled from