I presume that you wish to achieve this in BookWright Any image which covers the page number will eliminate it. So try this: Create a small image box large enough to cover the page number. Create an image file in your image processing software and fill it with a colour the same as the page from which you wish to delete the number. Upload to Bookwright and add the image to your image box.
The process of removal from BookSmart is quite straightforward, enter the footer, delete the number and select "this page only". If the software engineers can do this with Booksmart, why not BookWright I wonder?