EPM (Enhanced Protection Mode)

I am using IE9 (Win7--64-bit). Why am I being asked to Disable EPM in Internet Explorer?  EPM was introduced in IE10 and 11!! I did disable Protection Mode in my settings, but each time I attempted to open a pdf document, the "...Disable EPM in Internet Explorer..." message would surface.  Any nuggets of wisdom?  I do not want to use IE10 nor IE 11.

Thanks   ep