Disclosed is methods for applying a radiation curable fluorescent varnish to a document and authenticating the document via the radiation curable fluorescent varnish. The ultraviolet radiation curable fluorescent varnish comprising at least one curable monomer or oligomer, at least one photoinitiator, and at least one fluorescent material, wherein upon exposure to activating radiation, the fluorescent material fluoresces to cause a visible change in the appearance of the ultraviolet radiation curable fluorescent varnish. The methods include determining a location of printed portions of an image on a substrate and digitally printing the ultraviolet radiation curable fluorescent varnish onto the substrate in image registration only upon one or more portions of the determined printed portions on the substrate.