1. Install 2. Uninstall Install Adobe Reader (If Flatpak is not installed) Install Flatpak on Ubuntu first.https://gangserver.tistory.com/333 - Manual install$ flatpak install flathub com.adobe.Reader [ Execution log ]gangserver@RC530-U0922:~$ flatpak install flathub com.adobe.ReaderLooking for matches…com.adobe.Reader permissions: ipc x11 multiarch file access [1] t..