My company sells Zebra Android devices that we install our own app on (the devices are like a phone, but with scanners and more durable hardware). We can order the devices with the GMS or AOSP operating systems. If we order AOSP then there is less setup, but we would have to load a PDF reader on the device. One solution is to side-load Google's PDF Viewer from APKMirror before distributing the devices to clients.
Since APKMirror states that they manually verify each apps signature I am not too worried about security, but I am confused about how this is licensed. I opened "About this Viewer" from within the app and saw a plethora of Open Source licenses, which all say the app is free to use and distribute. However, I thought all apps provided by the Play Store were licensed only to the individual downloading the application. IE - APKMirror would have to violate the license to generate the APK, unless they received an APK directly from Google.
I understand that each app developer is responsible for licensing their application independently. So, in general, is it enough to verify the signature of the APK from APKMirror and read the license agreement within the app itself to verify that the app is ok to redistribute?