We wrote a 32 bit application that uses a WPF webbrowser control to view html pages. In some of the html pages, we have links to pdfs that launch in a separate internet explorer window. We recently switched to a new version of Adobe Reader DC as the default pdf viewer and noticed issues loading pdfs. The IE window launches from the application, but it shows a blank screen and an error eventually pops up. If you use internet explorer instead of the app to view the html page and select the pdf link, a new window showing the pdf is displayed correctly.
The problem can be avoided if I turn off protected mode in Adobe Reader. But, circumventing the security sandbox doesn't seem like a good long term solution. Also, the problem seems inconsistent. It works fine on some PCs with protection mode on and not on others. All PCs were tested with different versions of Windows 10 ranging from 1607 to the latest.
I've spent days trying to find a solution. As far as I can tell, the settings for IE and Adobe Reader DC are the same on all PCs. I even resorted to exporting and importing all registry settings for these items. I also tried enabling a custom policy mentioned at Protected Mode — Acrobat Application Security Guide . Any clues would be appreciated.