Hi,
As you're using a template you'll nedd to add the page break manually; using 'page-break-before' style and replaceTemplateVariableByHTML. Something like:
$html= '<p><span>This is a page</span></p><p style="page-break-before:always;"><span>This is other page</span></p>';
$docx->replaceTemplateVariableByHTML('VAR', 'inline', $html);
Regards.