jQuery one-liner :
$('a[href$=".pdf"]').attr('target','_blank');
Also in vanilla Javascript :
[].filter.call(document.querySelectorAll('a'), function(a){
return a.href.match('\\.pdf$') ? a.target = '_blank' : 0;
});
Or maybe :
var anchors = document.body.getElementsByTagName('a');
for (var i = 0; i < anchors.length; i++) {
if(anchors[i].getAttribute('href').match('\\.pdf$') {
anchors[i].setAttribute('target', '_blank');
}
}
Try it here : http://codepen.io/gabssnake/pen/KyJxp