There are a great many features to an Electronic Document Management (EDM) system, here are the 3 main benefits:
Multiple Index Fields
Allow you to store and search for a document based on any of the Index Fields created within a particular filing cabinet.
Encryption and Tracking
All documents are encrypted so they can only be accessed via the document management system. Even IT can't see the content of the documents unless they have access via the system. Every document is tracked from when it is placed into the system showing who did what and when.
A workflow passess the document from one person to another and tracks where in the workflow it currently is. The history of the workflow is stored against the document.