What would be the difference from what you describe and printing simplex. I
suspect you haven't selected duplex printing in your print driver.
Go to <File <Print <Properties
You will have non standard menus at this point. Here are two
possibilities:
Scenario 1
Go to the <Finishing Tab
Check <Print on Both Sides
Select <OK <OK
Scenario 2
Under Document Options select <Print on Both Sides
Select <OK <OK
also look for Layout and advanced tabs
If what you mean is that it looks like every other page is missing, then
perhaps the support your printer has for duplexing is to print on one side,
take the papers out and turn them over (possibly reversing the order) and
then loading them in the tray and printing on the other side.