No, you do not have to copyright your work unless your school requires you to do so. However, in order to file a suit for infringement you will need to have your copyright registered. We provide copyright preparation services at a cost of $75.00 per document. This is available at the time of submission only. Once we begin to process your dissertation/thesis, we can no longer file on your behalf.
If you'd like us to submit on your behalf, you can withdraw your submission, and resubmit. However, this will effect your submission date.
If you wish to file for copyright registration independently, you will need to contact the U.S. Copyright Office at 202-707-6787 or http://www.copyright.gov/help/general-form.html.