To enhance online security, Microsoft introduced an Enhanced Protected Mode (EPM) in Internet Explorer 10 and later. Because of certain restrictions EPM enforces, displaying a PDF in IE with Acrobat or Reader can require turning off EPM. Some versions of IE had EPM enabled by default. Current versions have EPM disabled by default.

Acrobat products only partially supported EPM with 10.1.8 and 11.0.04. With those versions, incompatible add-ons are automatically disabled when EPM is on. If you encounter a site that needs an add-on such as an Acrobat plug-in, disable EPM for the specific website. Then, you can use the site while having EPM enabled for the rest of the Internet. Only disable EPM for websites you trust.

• To disable EPM for a single site, click the Disable button when the EPM message bar appears.
• To disable EPM entirely, see http://support.microsoft.com/kb/2864914

Full support is provided with 10.1.9 and 11.0.06.

• The latest enhancements are detailed in the Release Notes. 
• 11.0.07 changes: A 64-bit plug-in was created for IE 11 with Enhanced Protected Mode on in Win 7.

When you open a PDF when Reader's Protected Mode is off and EPM is on in IE 10 or 11, Protected Mode is enabled automatically. Protected Mode is on even if the user settings and the preferences user interface indicate that Protected Mode is off.

The current experience

If you have Acrobat DC Continuous (Subscription)

Starting October 2016 update of Acrobat DC Continuous

You can always download a PDF locally and view it in the desktop application. You can also open a PDF in IE.

Note: With Acrobat DC Continuous (October 2016 update or later), a PDF can easily be opened in IE irrespective of whether the EPM is disabled or enabled.

If you have Acrobat DC Classic (Desktop only), Acrobat XI, or a previous version

You can always download a PDF locally and view it in the desktop application. However, when a PDF is opened in a browser, a dialog or message bar appears that provides options for action (the message varies by context):

“This web page wants to run (Adobe PDF Reader | PDF Browser Control | AcroPDF.dll). If you trust this site, you can disable Enhanced Protected Mode for this site to run the control.”

The notification includes options such as: 

• Run Control | Don’t Run
• Disable | Always Ignore
• OK | Cancel

The behavior is as follows:

• Choosing to allow results in the PDF loading. The notification reappears each time the PDF is reloaded.
• Choosing to not allow cancels the PDF loading process, and this prompt doesn't reappear for that domain unless the user deletes their browsing history.
• Taking no action results in a blank web page.
• On LiveCycle forms, choosing to not proceed results in not loading the PDF and the following warning appears:

Other issues

3597910 Windows 8 Only: Web Capture (save HTML as PDF) user interface items do not appear in the IE UI.

Workaround for 32-bit machines: If you manually create a folder named "Low" in the cache directory under %USERPROFILE%\AppData\Local\Packages\windows_ie_ac_001\AC\INetCache, it starts working.