Hi Patti
1. File management - PDF/DOC/XLS type files that would have permissions set per group. Namely, corporate personnel docs storage or integration with a repository where these types of files could be stored. (We have used DocMan in standard Joomla).
In Jomsocial there is a feature called group discussions this can be set to allow file uploads and the file types depend on what you set in joomla file types. This method works well for files but if you are looking for a document management system then this is not that. If a group is private then unless you are a member of that group you cannot see the discussion.
2. Ability to attach files, videos to a message.
This is not possible and would require custom development
3. User permission management - what are the limitations (i.e., visible/not visible, or add/edit/delete at user level). If there is not inherent in the current JomSocial Pro, is it possible with an addon or extension?
Jomsocial Does not use Joomla ACL, that will be added in JS3.4 but it does manage privacy and user levels very well within its self
4. What is the expected support turnaround on standard support questions that meet your support criteria?
Support questions are answered within 24 hours and this depends on where you are in the world. We have good coverage world wide. You would normally get an answer anytime from 1 hour to 4 hours
5. Do you have a community of extension/customization individuals that we can work with?
The only link we have is to osdesk they are developers and not our own. custom work is not offered by us or supported in our forum
www.jomsocial.com/jomsocial-developers