Download, Store and Open Huge document (Word, PPT, Excel, PDF)

I have an app that so simple, just have login and authenticate function, after that user can retrieve all document through a web service api, store it automatically and can receive notification when it has an update file.

So the question is, what database can I adapt to this project, because it is very huge (maybe ~5Gb to be stored in locally), can work offline (read-only) and synchronize when phone is connected to internet.

I am very appreciated for your support!