Here is how to print from Adobe Reader back-to-back.
Open up file, go to Menu bar, File, Print.
If the following window comes up at any time, click on the checkbox that says Do not show this message again. Then click on Yes.
Print window appears. Click on the Printer button toward the bottom LEFT of page, next to Page Setup
The next dialog box make a checkmark next to Two-Sided. Then Click on Print. (It does not print yet!)
Hope this helps!