The default setting for library documents is Public Access (no restriction).  

To restrict access for a document:

1. Click the Library Documents link in the Feature List/Administer menu.
2. Select the document from the Document List.
3. Click the Restrict Access radio button and click the OK button.
4. Select the organization name(s) from the Organization List and click the Add button to move to the right-hand list.
5. If you want to restrict access to certain groups within the organization, select the organization name in the right-hand list box and click the Restrict Access to Group button.
6. Select the group from the Limit Access To drop-down list and click the OK button.
7. If you want to add another group to the access list, repeat steps 5 and 6.
8. If you want to allow access to all groups in the organization, repeat steps 5 and 6, but select All Groups from the Limit Access To drop-down list.