Before adding protection to a document, you can specify certain parts of the document where you want to remove the restriction and allow a particular user or group of users to modify these parts.
Select a part of a document to be unrestricted.
Click the Range Editing Permissions button on the Protect section.
In the invoked Editing Permissions dialog, select a user or group of users to be allowed to edit the selected part of a document.
Editable ranges will be highlighted and enclosed in brackets.