The invention concerns a sheet-by-sheet flexographic printing device of safety documents, comprising means for transferring (2) said sheets (F), successively, from a supply station (1) located upstream, to a storage and removal station (6) located downstream, via at least a flexographic printing station (3) adapted to process the front surface of said sheets called first station. The invention is characterised in that the device also comprises at least a flexographic printing station (4), called second station , adapted to process the back surface of said sheets (F) during their transfer from upstream to downstream, without having to grasp them and modify their orientation between the two stations, said two stations being separated by at least two intermediate cylinders (22, 23) and said second printing station (4) is offset in height relative to the first (3), such that when they are transferred from one to the other, the sheets (F) are imparted an upward trajectory. The invention also concerns the security documents obtained by using such a device.