When printing to a Xerox 6605dn, the options for double-sided printing and print quality are several clicks away. Here's what to do:
Step 1: Once you are ready to print your document, and have selected File -> Print, choose the "Options" drop-down below the "Orientation" section, and change this selection to "Xerox Features".
Step 2: Once "Xerox Features" is selected, an additional drop-down will appear (set by default to "Paper Output"). Underneath this dropdown will be several selections including Job Type, Paper, 2-Sided Printing, and Print Quality. Under "2 Sided Printing", change this from "1-Sided Print" to "2-Sided Print".
Step 3: Click the blue "Print" button at the bottom right to print your job.