title: Tile/concatenate high resolution PDF files with imagemagick
body: <p>I've 9 high quality PDF files. I want to merge them into one large PDF of 3x3. I then want to turn this into a PNG file. I want to keep the resolution/sharpness during this process so that on the resulting PNG I can zoom right in and still see the fine detail. I thought I might do this with imagemagick but I'm struggling. Any ideas please?</p>
  
  <p>I've tried this to merge them together to start with. It works, but the quality doesn't remain.</p>
  
  <pre><code>montage input_*.pdf -background none -tile 3x3 -geometry +0+0 output.pdf
  </code></pre>
  
  <p>Please note that file size and size of resulting image isn't an issue. I've no need to print it or anything like that. It's for viewing on a computer only.</p>
  
  <p>Here is a sample of three of the PDF files:</p>
  
  <p>1) <a href="https://www.dropbox.com/s/qc094jg1nkfk0jw/input_1.pdf?dl=0" rel="nofollow">https://www.dropbox.com/s/qc094jg1nkfk0jw/input_1.pdf?dl=0</a></p>
  
  <p>2) <a href="https://www.dropbox.com/s/gb4u8r7bxg8lw2r/input_2.pdf?dl=0" rel="nofollow">https://www.dropbox.com/s/gb4u8r7bxg8lw2r/input_2.pdf?dl=0</a></p>
  
  <p>3) <a href="https://www.dropbox.com/s/97dhi42wrvfxfd2/input_3.pdf?dl=0" rel="nofollow">https://www.dropbox.com/s/97dhi42wrvfxfd2/input_3.pdf?dl=0</a></p>
  
  <p>Each PDF is 1071 x 1800 pts (using pdfinfo).</p>
  
  <p>Thanks</p>
  
  <p>James</p>