A device for illuminating an existing sign (100) having a specific given pattern on its front side, and a method of manufacturing such a device. A removable laminate (102) is intended to be applied to the front side of the sign, and comprises a mainly transparent cast compound or matrix (200) and a number of light emitting diodes (104) embedded in the matrix together with associated connected diode wires. The light emitting diodes are positioned in a specific pattern adapted to the existing pattern of the sign. Furthermore, a control unit (110) is configured to provide the light emitting diodes with electric current from a source of power supply (112) connected to the control unit, and to control the current feeding to the light emitting diodes in accordance with a predetermined scheme.