A printer system for printing pages belonging to an interactive page system includes a cartridge comprising a data storage area in which is pre-stored a range of identifiers, each identifier being unique throughout the interactive page system; and a printer comprising an interface for receiving the cartridge, a reader for reading an identifier from the range of pre-stored identifiers, a coded data generator for generating a page identifier from the identifier, and a printing mechanism for printing the page identifier onto a page. The reader reads a previously unread identifier from the range of identifiers each time the coded data generator is to generate a page identifier.