1) Edit the Page/Post that you would like to hide header and Footer
2) Within the right side, you can notice a dropdown option to select the Page Attributes or Post Attributes
3) From the dropdown select Elementor Canvas and Update the Page or Post that your viewing.
4) That’s it, now theme’s default header and footer are removed automatically and the page that you designed with Elementor will be shown in full view by removing header and footer.