How do I duplicate a page?

If you mean how to duplicate a form, please follow the steps here: 

https://www.jotform.com/help/42-How-to-Clone-an-Existing-Form-from-a-URL

https://www.jotform.com/help/27-How-to-clone-an-existing-form-from-your-account 

If not, please give us a bit more details about what you are trying to copy.