What can't I print double sided?

I am a Mac user with Adobe Acrobat X.  When I want to print double sided the option is greyed out and not available to me.  I have seen that a lot of people have this issue and it seems to be a design flaw with Adobe.  I can print double sided with Word, just not any Adobe PDF.  All of the responses I've seen have not been helpful; they mostly tell you the steps for double-sided printing, which I already know.

Is this a driver issue?  Is there a new driver I need to download?