Hello,

Do you have an idea to but in bold chapitrenbr and titre in italic ?

@bottom{
	content: "CHAPITRE " string(chapitrenbr) " | " string(titre);
}

This cannot be done with generated content, you will need to take an element from the document instead:

@page {
  @bottom { content: flow(footer) }
}

div.footer { flow: static(footer) }

...

<div class="footer">
  CHAPITRE
  <b><span style="content: string(chapitrenbr)"></span></b> |
  <i><span style="content: string(titre)"></span></i>
</div>

Thank you