A method of revealing hidden content associated with printed content using a handheld display device. The method includes the steps of: imaging an area of a printed substrate and generating image data using an image sensor; determining interaction data using the image data; retrieving display data using an identified page description, the display data including the hidden content associated with the printed content; displaying, on an opaque touch-sensitive display screen of the handheld display device, display information based on the display data and including the hidden content. The opaque display screen has real-time virtual transparency through the screen to the printed content from a user's perspective to provide a virtual window to the printed content. The opaque display screen additionally displays the hidden content in real-time as if it were printed on the printed substrate.