To set an Archive date…

Note: You can also multi-select multiple documents in a Document Type or multiple stacks in a Stack Type and set the date value for this field. You can also Right-click and choose the option Set Expiry date to set the value.

This is currently not possible.

You cannot unarchive a Document or Stack, once it is marked as Archived.

You can manually delete Documents and Stacks in the Archive DB. Once a document/Stack is archived, a security label is applied. Now only users with the Delete privilege in the Security Label can delete data and documents in the Archive DB. You can also use the Expiry Date feature.