Ask HN: Open Source approach to distributed repository

Does anyone have thoughts on how to approach this applications? We may be willing to contribute monetarily to a good open source approach. Application: Repository for Sales Presentations, Catalogs, and Documents Documents: PPT, PDF, Word (Can convert to PDF, but not ideal)

Platform: IPAD (Required) ; Android Tablet (Desired); OS X (Desired)

     Requirements:

1) Synchronization between server and remote copies for offline mobile presentation (2GB of files) 2) Permissions/Group structure for multiple groups and users. 3) Ability to log document views on remote device then upload data to server

4) As much as possible open source (widely used platform) or low cost cloud storage.

5) Unviewed files highlighted.

     Desired:

1) Keyword Searchable 2) HTML5 Based 3) The ability to create a sales presentation session and send download links to a customer.