1. An apparatus for capturing images of a document and interaction of a primary user with the document in an interaction session, the apparatus comprising: image capture means adapted to capture an initial image of the document and at least one subsequent, additional image of the document during an interaction session, the image being mapped to a known co-ordinate system; interaction capture means for capturing the interaction of a user with the document, whereby the interaction capture means determines at least one co-ordinate of a pointer used for the interaction relative to the same co-ordinate system defined for the initial captured image; and processing means for determining an appropriate transform that maps the additional image onto the original image.