You can ignore format control commands for Line Printer Remote (LPR) clients and always assign the RAW datatype by editing:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LPDSVC\Parameters

Add Value name SimulatePassThrough of type REG_DWORD and set it to 1.

A data value of 0 (the default), instructs the LPD service to assign a datatype based on the control commands.