change permissions on a file or an item, open the manage permissions
page for that file or item and select the name (or names) of the user or
group for which you want to change the permissions. Then click the Edit
User Permissions button in the Modify section of the Permission Tools
ribbon. The Edit Permissions dialog appears, enabling you to select
permissions for that user or group (see Figure 1).
Figure 1. Changing a user’s or group’s permissions.
the Edit Permissions dialog, you can select one or more permission
levels. For example, if you select Contribute and Approve, the user will
be able to both edit the document or list item and approve it but will
not be able to set the permission on the file or item. When you are done
selecting permissions, click OK.