There are a couple of different things to check when this option is not available. The first of which would be to do the following.
To resolve this you need to do the following:
- Remove the current driver
- Use the “Find Any File” app and delete all files with the word Xerox in it, including hidden files.
- Also delete the Xerox folder from the Printers folder on the machine
- Install the latest driver
If this does not resolve the issue you can enable the option threw macs cups utility (This is not supported).
- Open safari and in the address bar type 127.0.0.1:631 (if nothing comes up you will need to enable CUPS, see macs website)
- Once open choose "Printers" and click on the installed printer in question
- In the new screen in the Administration dropdown choose "Set default options"
- Select "Paper Output"
- Here you will find the option for 2-sided printing.