W3C is thinking about everything.
For printing pages you need very different rules from those used to display content in the browser. For example, you’ll want to declare fixed sized pages rather than lay out a continuous flow of text. Books also need many specific elements for the printed layout: margins, running headers, page numbers, a table of contents, and so on.
This is a companion discussion topic for the original entry at https://www.pagedjs.org/documentation/03-w3c-specs/