Add Field to all pages like title, url and position

I want to add one text field named as custom url for all pages. Please suggest steps for it or provide example.

Thanks. But i want that custom url field yml code at only one place which should work for all pages. I dont want to add field seprately in blueprint of every yml.

You have to, of course you can define once and reuse, but you still have to add the field.

How can i add field below Template field in page creation popup?