Epson recently released a driver update for OS X 10.9 Mavericks which automatically shows up within the Apps/Software update menu. Like most users my wife dutifully added the update which then removed her duplex printing settings.
Notice the “Two-Sided” printing option is off and grayed out.
While I’m sure this was unintended it did pose a real problem. After reinstalling drivers and the printer itself several times I found the following fix.
1. Select “Printer Features” from the pull down menu (Hint: Click Layout)
2. From the “Feature Set” pull down menu select “General 6”
You’ll notice that buried within this sub menu is the option we’re looking for.
You can see in this screen capture I’ve already saved mine as “Duplex!”