I am a knowledgeable user. I am trying to set Adobe Reader as the default pdf reader. All defaults have been cleared and I am presented with a list of apps and the "just once or always" options . I select Adobe and tap always. I get this presentation whenever I attempt to open a pdf file. BUT if I choose any other app and tap always, that app is set to the default. The only one that won't work is Adobe
Android, General troubleshooting, View or share PDFs
Go to"Settings" --->>"Apps" --->> tap on the Adobe Acrobat icon --->> tap on "Set as default"
To verify go back to "Apps" and tap once on the three dots icon menu (a.k.a the more options menu), then tap on "Default apps". In this section , from top to bottom, check that "Browser app" has a default web browser selected.
Then also check below another selection below " Default app selection". Tap on it once.and make sure that you select "Ask before settings default apps" instead of "Set default apps automatically".
Now exit settings and go back to the Adobe Acrobat icon in your Home Screen.
Do a long press on this icon and select "App Info" from the context menu. Now tap once on "Set as default". and then tap once on -->>> "Go to supported URLs". select "In this app" from the context menu.
Now, to re-verify, go to "My Files" files explorer, navigate to "Documents, if you have any PDFs in that folder tap once on any PDF document there and it should open in Adobe Reader mobile app automatically.