User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:50.0) Gecko/20100101 Firefox/50.0 Build ID: 20161213214853 Steps to reproduce: I went to the menu in the top right corner. I clicked print. I clicked print in the top left corner. I selected a printer. I clicked the page setup tab. I changed two-sided from one sided to two sided Actual results: The pages came out of the printer one sided. Expected results: The pages came out of the printer two sided.