def header
      header = "%FDF-1.2\n\n1 0 obj\n<<\n/FDF << /Fields 2 0 R"

      # /F
      header << "/F (#{options[:file]})" if options[:file]
      # /UF
      header << "/UF (#{options[:ufile]})" if options[:ufile]
      # /ID
      header << "/ID[" << options[:id].join << "]" if options[:id]

      header << ">>\n>>\nendobj\n2 0 obj\n["
      header
    end
def header
      header = "%FDF-1.2\n\n1 0 obj\n<<\n/FDF << /Fields 2 0 R"

      # /F
      header << "/F (#{options[:file]})" if options[:file]
      # /UF
      header << "/UF (#{options[:ufile]})" if options[:ufile]
      # /ID
      header << "/ID[" << options[:id].join << "]" if options[:id]

      header << ">>\n>>\nendobj\n2 0 obj\n["
      header
    end
pp 559 https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/pdf_reference_archives/PDFReference.pdf