When downloading and installing the RhoE software, you will find a couple of folders: Documentation and APD Kit v2-19-06. In Documentation you will find overview and programmer manuals on APD (Adaptive Printer Driver) and the other folder contains the actual drivers (dll). APD is for interfacing with moble printers. Although its over a seral port, the port you will be using the port assigned to the BT device. In other words, once you pair and connect a comm port will be assigned to the device. This is the comm port you will be targeting.
In addition to documentation and dlls in the APD Kit v2-19-06 folder, you will find code samples and demo apps to help jump start development.
Hope this helps.