Build PDF for B5 pagesize

themes/cookbook/layouts/partials/printhead.html

@@ -2,6 +2,11 @@
     <meta charset="utf-8">
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <link rel="stylesheet" type="text/css" href="../../css/bulma.min.css">
+
+     <style id=page_style>
+      @page { size: B5; }
+     </style>
+
     {{ $title := print .Site.Title " | " .Title }}
     {{ if .IsHome }}{{ $title = .Site.Title }}{{ end }}
     <title>{{ $title }}</title>