A system is presented for transmitting document references or tokens between users of integrated wireless and wire-based communication services. The system includes workstations, files servers, printers and other devices coupled to a wire-based network. Mobile computing devices are coupled to the wire-based network through either IR (infrared) or RF (radio) transceiver gateways. Each mobile computing device appears to hold a user's collection of documents: the device is programmed to receive, transmit, and store document tokens. The system includes a token-enabled document server that uses digital signatures to provide secure transfer of document tokens between users of the mobile computing devices and email clients. The token-enabled document server operates independent of the identity of the holder of the document token. Only the issuer of the document token needs be registered with the signature based document server to properly authenticate document tokens.