I want to open Word, Excel, Power Point and PDF files on Android. However, I searched for an app for that, but I don’t know. So please tell me about the app. What you need is open source. (However, other than LibreOffice. I tried the app, but it didn’t work. Development is not progressing.)
I’m not aware of any open source app able to do that, apart from Libre Office (but it’s only a viewer, and experimental). If you take this requirement out, then yes.
Word for Android to begin with (for Word docs), or SoftMaker Office HD Basic for Android : free, with word processor, spreadsheet, presentations and database.
PDFs are easy. There are a ton of apps able to open them.
OnlyOffice and MuPDF.