I have bought a nice networked Brother laser that does duplex printing. It works well as our default invoice printer, and does single-sided printing via our Ubuntu/Openvpms server. 

The printer can print duplex when we select it in the printer options for an individual document (eg .odt or .pdf) from a workstation or when logged directly into the server. However, I cannot find an option in Openvpms or in the CUPS layout for duplex printing. I would like to set duplex as default for all documents. 

Any ideas?

Thanks,
Damien