title: Error using magick R to import PDF
body: <p>I have hundreds of PDFs that I want to crop. For each PDF, I have a unique set of coordinates around which to crop. I am trying to use the R's magick package (version ImageMagick 6.9.9.14), but I receive an error when importing a PDF.</p>
  
  <p>This example from the magick documentation throws an error:</p>
  
  <pre><code> library(magick)
   manual &lt;- image_read('https://cran.r-project.org/web/packages/magick/magick.pdf', density = "72x72")
  </code></pre>
  
  <p>The error I receive is "Error in magick_image_readpath(path, density, depth, strip) : Magick: PDFDelegateFailed `The system cannot find the file specified.
  ' @ error/pdf.c/ReadPDFImage/809"</p>
  
  <p>When I check the config settings:</p>
  
  <pre><code>magick_config
  </code></pre>
  
  <p>I find that ghostscript is true.  I am not sure if there are other settings required for reading in a PDF.</p>
  
  <p>Has anyone else encountered a similar problem with magick?  I am open to alternative packages with the ability to crop PDFs, if there are any.</p>