No access to Dropbox Shared Directory

My business has a Dropbox account with multiple users.  Each user has private folders, and there is a shared directory that all users access.

I need to enable users to be able to annotate pdf documents on the shared directory using their iPads.

When I link the Dropbox account to Acrobat Reader on my iPad, I can only access the private folders for that user. 

If I browse the shared directory in the Dropbox app on the iPad, open a document, and tap "open in Acrobat Reader", I just get kicked back to the private folders: