how to force download file pdf in partialjs (nodejs)

im working with partialjs and have question, how to force download with partialjs?

my codes do something like this:

html:

<a href="/media/document.pdf" class="download-button">Download pdf</a>

i use jquery filedownload, which is working well download 'zip' file for example, but failed on 'pdf' due to this kind of http header setting that i dont know where to set in the nodejs/partialjs.

javascript (jquery):

  $('.download-button').on('click', function(e) {
       e.preventDefault();
       var filePath =$(this).attr('href');   
       // jquery do something here
       //...
      $.fileDownload(filePath); 
  });

please enlight me..