Just downloaded the Google PDF Viewer to try and test (it's only 7 MB and no ads, plus I'm using NetGuard firewall) and, as I've had no other viewer and no default set - accidentally, or not - it, ofc., opens up a test PDF file; however, it is ''not'' listed anywhere in Default apps, or Opening links - and the app itself, Google PDF Viewer has nothing adjustable set, only a grayed out option for "Open supported links, Open in this app". All on Android 10, '''Q'''