Question
Acrobat Printing Double-Sided in spite of OS settings
Acrobat was refusing to respect my desire for single-sided prints, despite "2-sided" being unchecked in the Printer's dialog.
Solution: check and uncheck the setting from within Acrobat:
Print>Printer>(dismiss warning)>check/uncheck 2 Sided
Although every other app was printing single-sided, Acrobat didn't recognize the setting until it was done from within Acrobat.

Mojave (new), Canon duplex printer (2-sided capable)