title: Convert multipage PDF to a single image
body: <p>I have to convert a multipage PDF document to a .png image.</p>
  
  <p>I try with ImageMagick, but I cannot achieve final result:</p>
  
  <pre><code>convert document.pdf document.png
  </code></pre>
  
  <p>or</p>
  
  <pre><code>convert -adjoin document.pdf document.png
  </code></pre>
  
  <p>This command create N images .png (where N=num of page of document):</p>
  
  <pre><code>document0.png
  document1.png
  .... 
  document(N-1).png
  </code></pre>
  
  <p>I need, if possible with a single command, to obtain a single image.</p>