I'm not understanding what it is you're wanting to do: copy/duplicate the content on the page or something else? If you just want to duplicate the content, why not highlight, copy and paste the content into a new page?

Creating a new page will automatically duplicate the theme to that page.

If you want the layout and theme to unique, then duplicating isn't what you want to do, you would need to create a custom page template and upload that template into the folder for your currently active theme.