You could use the OpenNETCF.Net.Bluetooth library, still in development but
has enough functionality for you to achieve printing to a device.
First see this post for the most recent code drop and sample application:-
http://blog.opennetcf.org/pfoot/#ac9d82a04-e68b-4b39-8afe-4aa2e00acb46
There will be another update shortly which I'll also announce on the blog.
You'll need to do the following:-
Use BluetoothClient to discover devices to identify your printer
Get the BluetoothAddress for your chosen device - the DeviceID property of
the chosen device returned by DiscoverDevices
using BluetoothClient establish an outgoing connection to the device using
the BluetoothService.SerialPortService service Guid
Use GetStream to return the NetworkStream for the connection
Read and Write data from/to the stream
Close your BluetoothClient when you've finished.
As to what commands to send to your printer, that will depend somewhat on
the hardware and the documentation for your printer should help somewhat.
Peter