How to enable the duplex option in the driver/software; How do I duplex; How to set up duplex printing
If the printer has a duplex unit installed but does not print automatically on both sides of the page, check the driver/software settings on the computer to make sure the duplex settings are configured correctly. These settings tell the printer how to print the page and will override any settings on the printer. The duplex option must be added in the driver and then turned on to enable it to function. This is usually the case regardless of the data stream (i.e. PostScript, PCL) or operating system. Please follow the instructions below.
IMPORTANT! The screen shots and descriptions below apply specifically to the Lexmark T630 driver for Windows, but the instructions are similar for any of the laser printers.
Contacting Lexmark Technical Support
If you call Lexmark Technical Support for assistance with your printer, please be prepared to describe the problem you are experiencing, the message on the display, and any troubleshooting steps you have already taken to find a resolution. Please call from near your printer in case the technician asks you to perform a task involving the printer.
When calling for service, you will also need to know your printer model type and serial number. This information can be found on a label on the inside top cover of the printer. The printer serial number is also listed on the menu settings page(s) you can print from the operator panel.