Where is setting to open Adobe files in IE or not in IE (browser), In Adobe Preferences I see :
"use your browser to control viewing of PDF documents directly in the browser using Adobe Acrobat Reader xx or Adobe Acrobat xx. The following Adobe product is currently available for use by browsers:
c:\program files (x86)\Adobe\Acrobat 2015\Acrobat\Acrobat.exe
Thanks , ...