var downloads = document.getElementsByTagName('a');
for (i = 0; i < downloads.length; i++) {
    if (downloads[i].href) {
        var href = downloads[i].href;
        if (href.substr(href.length-4,4).toLowerCase() == '.pdf') {
            downloads[i].onclick = function() {
                pageTracker._trackEvent('pdf', 'download', this.innerHTML);
                location.href = this.href;
                return false;
            }
        }
    }
}