A handheld display device for imaging a printed substrate containing a printed form and for filling in the form. The device comprises: an optical sensor for imaging an area of the printed substrate and for generating image data; a processor for determining interaction data using the image data, the interaction data identifying a substrate identity; a transceiver for retrieval of display data corresponding to the form; and a touch-sensitive display screen for displaying display information based on the display data, the display information including a displayed form field of the form. The device is configured such that user interaction with the displayed form field via the touch-sensitive display screen enters form data into the device and causes a page description to be updated with the form data.