There is described a printing press (100) comprising a printing group (2) adapted to apply on a substrate at least one ink or varnish vehicle containing magnetic or magnetisable flakes and at least one magnetic orientation unit (10) located downstream of the printing group (2) along a path of the substrate, which magnetic orientation unit (10) includes at least one magnetic-field-inducing device (12) adapted to orient the magnetic or magnetisable flakes contained in the ink or varnish vehicle applied on the substrate to induce an optically-variable effect in the ink or varnish vehicle. The printing press (100) further comprises a drying/curing unit (15) located along the path of the substrate and cooperating with the magnetic orientation unit (10), which drying/curing unit (15) is adapted to dry or cure the ink or varnish vehicle applied on the substrate following orientation of the magnetic or magnetisable flakes. The drying/curing unit (15) is mounted on a movable supporting structure (16) that is adapted to move the drying/curing unit (15) between a working position (WP), where the drying/curing unit (15) is cooperating with the magnetic orientation unit (10) and which is located proximate to the path of the substrate next to the magnetic orientation unit (10), and a retracted position (RP), where the drying/curing unit (15) is retracted away from the magnetic orientation unit (10) and from the path of the substrate.