It hangs only with digitally signed pdf, sometimes nothing opens but the app is freezed (you have to kill it from task manager) ,some others signed files seem to open but hangs ("not responding"). All windows 10 clients( 12) and RDS 2019 (each with 2021.005.20060 ver) have the same problem. Tested new 64x ver (also 2021.005.20060) , same result.
Nothing is logged in Event Viewer (Application, Installation or System).
Other test : Uninstalling / Installing ver 2019.008.20071 with AdobeUpdate service disabled, but same result (hang or freeze).
Disabling protected mode at startup does permit to open some of signed pdf, but in a very slow way.
All these problems started at the end of July.
Chrome and Edge are able to open these signed pdf files without problems.
We are sorry to hear that. As described the application is freezing and not opening when you try to open the digitally signed PDF files.
As mentioned you have tried installing the latest version / removing the application and reinstalling with no success. Though disabling the protected mode works but is very slow.
Please try to turn off the protected mode as below and see if that helps: Go to Edit > Preferences > Enhanced Security > Uncheck 'Enable protected mode at startup' Turn off the protected mode and uncheck enhanced security > Click OK and reboot the computer. Note: Please turn on the security after testing to avoid any security risks.
Also try to add the files and folder to Adobe Acrobat Reader list. Go to Edit > Preferences > Enhanced Security > Add File and Folder path to Adobe Acrobat and click OK and reboot the application.