What To KnowIn Acrobat, got to Edit > Preferences > Internet > Internet Settings > Programs > Manage Add-Ons > Adobe PDF Reader > Disable.It's a good idea to disable auto-open on Adobe Reader because attackers have been known to use it to run malware.
This article explains how to stop Adobe Acrobat Reader from automatically opening PDF files in your web browser by default. Instructions in this article apply to Adobe Acrobat Reader DC and Internet Explorer 8 and later.
How to Keep PDFs From Opening in a Browser
Follow these steps to prevent Adobe Acrobat Reader from opening PDFs within your web browser:
Open Adobe Acrobat Reader and select Edit > Preferences in the menu bar.
You can also bring up the preferences menu with the keyboard shortcut Ctrl+K (or Command+K for Mac).
Select Internet in the left pane of the preferences window, and then select Internet Settings.
Select the Programs tab.
Select Manage Add-Ons.
Select Adobe PDF Reader in the list of add-ons.
If you don't see Adobe PDF Reader listed, try selecting Run Without Permission from the Show drop-down menu.
Select Disable so that the PDF Reader won't open PDFs in the browser.
Why You Should Disable Auto Open in Adobe Acrobat Reader
Attackers have exploited Adobe Reader's confirmation-free rendering to spread malware. Turning off the Adobe Reader add-on for Internet Explorer helps you avoid accidentally downloading a computer virus via the internet.