title_body: Do epub 3.0 pagebreaks always require an id? Is it within the EPUB 3.0 specification to have a pagebreak span without an id?
  
  I.e.
  &lt;span epub:type="pagebreak" title="2"&gt;&lt;/span&gt;
upvoted_answer: Pagebreaks are usually used in conjunction with nav document page-list sections and since you need an id to refer to pagebreak markers in the book it'd be rather pointless to use pagebreaks without ids and a corresponding page-list section.
  
  You can find an IDPF-approved sample epub3 book with pagebreaks and a page-list nav section here.