Regular page numbers don’t work for a digital magazine with up and down scrolling pages and the reader cannot guess how long the article is. There are no generally accepted principles of designing page footers, although more magazines are using paginate or page numbers. It’s good form to paginate vertical pages.
There are 2 ways of numbering pages: either use software pagination or design a custom page footer . It’s important to not only show the number of pages but also indicate how far through an issue readers are .
Check my other posts about interactive features and have a look at the Navigation Pages: