I nowadays I don’t see much benefit of dedicated Android apps in these cases (clients of hosted content). If your webapp works well for mobile browsers than making it a pwa is not much more than adding a single file and it feels pretty native to me. So you safe tons of development work. Or am I missing on something?
Do I understand correct that it is a document manager, specialized on PDFs? I tried various EDMs for personal use (e.g. Mayan, paperless), but was never really happy, so maybe I find time to give it a spin.