title: Why some pdf files are not recognized as pdf in android devices
body: <p>I am accessing this <a href="http://www.mdpi.com/2077-1444/5/3/814/pdf" rel="nofollow">URL</a> with my android device and the pdf download starts downloading automatically, without asking me to open the pdf vieth the pdf viewer.</p>
  
  <p>This works in other websites.</p>
  
  <p>I am the developer of the website. I set up the header to application/pdf. Any idea what can be the problem? Thank you.</p>