This is perfect for when you have a lot of registered users and administrators on your site and want only certain users or administrators to have access to a document in the virtual filing cabinet. If you wish to do this, the directions are as follows:
Login to the backend control of the website by going to www.yourdomainname.com/administrator and entering your username and password.
Go to Components > Docman > Groups
Click the new icon 
at the top right of the page.
at the top right of the page.Enter the name of the group in the Group Field. The Description field below that is optional.
Now click on the Members tab (located at the top of the fields) to assign the users you want to this group.
Now click on the Members tab (located at the top of the fields) to assign the users you want to this group.
You will see everyone that has created an account on your website on the left side of the page.
Highlight everyone you want to be a part of this group.
Click the right arrow to transfer them over to the field “members in this group,” located on the right of the page.
Once done, click the Disk Icon
to save the page, located at top right of the form.Now you want to assign that group to a certain document.
Go to Components > Docman > Documents
We will assume you already have a document there to apply the group to.
Click on the title of the document you want to assign this user group you created to.
Click on the permissions tab.
In the viewers drop down menu you now see, choose the group you want to assign to this document.
In the maintainer drop down menu below that, choose the group you want to assign to this document to maintain it.
Once done, click the Disk Icon
to save the page, located at top right of the form.