title: Merge / convert multiple PDF files into one PDF
body: <p>How could I merge / convert multiple PDF files into one large PDF file?</p>
  
  <p>I tried the following, but the content of the target file was not as expected:</p>
  
  <pre><code>convert file1.pdf file2.pdf merged.pdf
  </code></pre>
  
  <p>I need a very simple/basic command line (CLI) solution. Best would be if I could pipe the output of the merge / convert straight into <code>pdf2ps</code> ( as originally attempted in my previously asked question here: <a href="https://stackoverflow.com/questions/2507596/linux-piping-convert-pdf2ps-lp">Linux piping ( convert -&gt; pdf2ps -&gt; lp)</a> ).</p>