Open Internet Explorer, and choose Tools > Manage Add-ons.
Internet Explorer 11 uses an ActiveX based plug-in. Follow the steps below to configure Internet Explorer to use the Acrobat/Acrobat Reader plugin for viewing PDFs:
Open Internet Explorer, and choose Tools > Manage Add-ons.
Under Add-on Types, select Toolbars and Extensions.
In the Show menu, select All Add-ons.

In the list of add-ons, select Adobe PDF Reader.
If you do not see the Adobe PDF Reader add-on, try the other options on the menu. For example, on some systems, the add-on appears when you select Run Without Permission.
Click the Enable or Disable button (it toggles depending on the status of the selected add-on):
Enable sets the Adobe PDF Reader add-on to open PDFs in the browser.
Disable turns off the add-on so it does not open PDFs in the browser.
