title: How to add an external resource (pdf file) in my doxygen documentation
body: <p>I generate a doxygen documentation. In one of my "page" I have a link to a pdf file:</p>
  
  <pre><code>&lt;a href="../documents/xxx.pdf" target="_blank"&gt;&lt;b&gt;Overview&lt;/b&gt;&lt;/a&gt;
  </code></pre>
  
  <p>This file is in my project in another directory. The documentation ends up in folder called "html". </p>
  
  <p>How do I tell doxygen to copy the pdf file into html ? </p>