NemakiWare is designed for this.
- You just store your files, organize them.
- You can search by filename or content. For instance, if a PDF or Word file contains "ECM", then you will find it by typing "ECM" in the search box.
- You can create groups, and set folders/files to only be viewable (or modifiable) by certain groups.
- You can update/modify documents, of course.
- All of this via the web interface. You may also choose to use NemakiWare's desktop sync client (Dropbox client clone).
You can install NemakiWare on your own server (or rented server), but a cloud service is also available (at a cost).
Bonus: It is open source.
Disclaimer: I work at the company that makes NemakiWare.