After the refactoring of the wkhtmltopdf engine, the headers/footers are managed in a very different way to be able to call wkhtmltopdf only once. The subst JS function must select the right header/footer corresponding to the current page company. However, a <div> was suppressed during the process and then, some external customization might be ignored (see github issue for more details). -issue: https://github.com/odoo/odoo/issues/19544