Brother MFC-9120CN - Manual (Page 137)

Printing and Faxing
129
7
Duplex Printing
7
 Manual duplex
Select Paper Handling.
• (Mac OS X 10.3.9 to 10.4.x)
Choose Even numbered pages and print, and then choose Odd numbered pages and print.
• (Mac OS X 10.5.x to 10.6.x)
Choose Even Only and print, and then choose Odd Only and print.