The slimjet browser based on Chromium which can enable NPAPI plugins in the setting menu and work well.
http://www.slimjet.com/en/whatisnew.php

Acrobat plugin loaded but did not display the PDF file (display "initialing...." only) both in Opera beta 36.0.2130.29 and Opera developer 37.0.2163.0, but it worked perfectly in Opera released version 35.0.2066.92, please kindly check and verify it, thank you in advance.

OS: windows 7 x64.
Acrobat version: 11.0.15
Have disabled #disable-npapi under opera://flag/