如何使用wkhtmltopdf在页眉/页脚htmls中进行页码编号？

I'm developing an electronic invoicing system, and one of our features is generating PDFs of the invoices, and mailing them. We have multiple templates for invoices, and will create more later, so we decided to use HTML templates, generate HTML document, and then convert it to PDF. But we're facing a problem with wkhtmltopdf, that as far as I know (I've been Googleing for days to find the solution) we cannot simply both use HTML as header/footer, and show page numbers in them.I'm developing an electronic invoicing system,