How to use Open Atrium 2 for document managment
The 2.30 version of Open Atrium supports folders out-of-the-box through the oa_folders module.

On earlier versions I have used a customized news section type and calling it Folders or Filesharing. With a clear workflow established with the people working on it, you can then have each document page being a folder, where all space members can add or remove further documents. It was obviously a limited solution, but made the purpose. Now we have a better OA world :)