Reopen a new tab in same window

You could simply set the target attribute as blank in the hyperlink redirecting to the PDF and it will open the file in a new tab. Something similar to this :

<a href="http://mysite.com/files/test.pdf" target="_blank"></a>

If you want to use JQuery for this, you can try something like this :

$(document).ready(function() {
  $("a").click(function() {
   link_host = this.href.split("/")[2];
   document_host = document.location.href.split("/")[2];

   if (link_host != document_host) {
     window.open(this.href);
     return false;
    }
  });
});