I have Adobe Acrobat Reader DC (version 2021.001.20155) installed. I've followed the instructions in this thread to get PDF files to open in one window but that is NOT happening. I even went so far as to reinstall adobe Acrobat Reader DC (version 2021.001.20155) and have the setting in Preferences set as shown to have PDF files open in one window but they continue to open in separate windows. I have restarted the software multiple times and have evn restarted my computer. This used to work and I don't know what happened. My computer is running Windows 10.