title: Disable cache links issue
body: <p>I have a site for download files (.pdf, .rar, .jpg,...).
  I have a big problem with server and I think it related to apache:</p>
  
  <p>For example i linked to 12.pdf for download it:</p>
  
  <pre><code>&lt;a href="12.pdf"&gt;book&lt;/a&gt;
  </code></pre>
  
  <p>It works fine but problem:
  I changed 12.pdf with another file with same name. When downloaded new 12.pdf, Previous file is downloaded.
  Even I remove 12.pdf from server and press Ctrl+F5 in my page, When clicked on above link, 12.pdf download start and file download completely!! Whereas not exist file with 12.pdf name on server.
  What is problem? Does apache cache my links? How solve this problem?
  My server OS is CentOS.</p>