n docs mod apk:

On Android, N Docs helps you to access, create, and edit documents. No connection to the internet is needed.

Microsoft Word(DOC/DOCX, password protected file, not supported)
Microsoft Excel(XLS/XLSX, No Password Protected File Support)
Microsoft PowerPoint(PPT/PPTX, Password Safe File Not Support)

Writer for Open/Libre (Open with thirdparty app)
Open/Free Calc (Open with thirdparty app)
Impress Open/Libre (Open with thirdparty app)