David Kimura PRO said over 2 years ago on Creating PDF files with WickedPDF :
  This is an exert from their documentation examples.

pdf = WickedPdf.new.pdf_from_string(
  render_to_string('templates/pdf', layout: 'pdfs/layout_pdf.html'),
  footer: {
    content: render_to_string(
  		layout: 'pdfs/layout_pdf.html'

Notice that the footer is being passed as a second parameter to the WickedPdf.new.pdf_from_string. In your example, it is getting passed into the first parameter and not the additional options.