I encountered a situation where I had to use footers and headers in my generated PDF printounts. CSS solution works for the first page only. And the only information I found is
Wkhtmltopdf does support even very complex headers and footers.
wkhtmltopdf.exe -T 50mm --header-html www.google.com www.stackoverflow.com test.pdf && test.pdf
That command uses the page at www.google.com as a 50mm header for www.stackoverflow.com for every page.
Note: If you use a custom page for the header/footer, you need to add in the beginning of your header/footer HTML!