title: HTML to PDF page does not converting properly with A4 page size
body: <p>I'm new b rails, I have successfully produced PDF from the HTML with wkhtmltopdf[0.11.0 rc1] free version, using ruby on rails(3.1).
  <br/>
  I want that PDF in A4 printable size. (PDF have multiple pages.)
  <br/>
  but it seems generated PDF having small size <br/><br/>
  my HTML wrapper/main <code>DIV</code> having  <code>width: 580px;</code> and wrapper <code>DIV</code> is centered By <code>margin: auto;</code> 
  <br/><br/>
  I'm already using Wicked-PDF and facing this issue in the generated PDF. using page_size as A4.</p>
  
  <pre><code>pdf = WickedPdf.new.pdf_from_string(render_to_string(
               template: 'assessment_reports/assessment_report.html.haml', 
               layout: "layouts/reports.html.haml", 
               handlers: [ :haml ], margin: { :left =&gt; "5mm",:right =&gt; "5mm", :top =&gt; "20mm", :bottom =&gt; "0mm" },
               locals: { :@view_mode =&gt; "pdf" }
            ))
  </code></pre>
  
  <p><br/><br/>
  <strong>Que is-</strong> how do i convert/scale its width- 210mm(which is width of A4 paper) and height proportionally while generating pdf? <em>Not require but if possible-resolution should 300DPI.</em>
  <br/><br/></p>
  
  <p>Any help would be appreciated.</p>