One of the goals of AgileRoadMapp is to simplify your product development processes. With that in mind we didn't want to create yet still another document repository. So you can access and work on your files from the applications that you already use (Google, Dropbox).
If you need to share a document from within AgileRoadMapp then you can simply associate a document from Google Drive or Dropbox to one of your products. Associated documents from Google Drive or Dropbox link back to the document in those cloud platforms.
We do not store a copy of those documents in AgileRoadMapp which simplifies your security and regulatory compliance processes as your documents are in one secure cloud system.