fix PDF print ref

Author: tomkralidis

docs/presentations/foss4g2024/index.html

@@ -24,7 +24,7 @@
 			var link = document.createElement('link');
 			link.rel = 'stylesheet';
 			link.type = 'text/css';
-			link.href = window.location.search.match(/print-pdf/gi) ? 'css/print/pdf.css' : 'css/print/paper.css';
+			link.href = window.location.search.match(/print-pdf/gi) ? '../default/css/print/pdf.css' : '../default/css/print/paper.css';
 			document.getElementsByTagName('head')[0].appendChild(link);
 		</script>
 		<link href="https://fonts.googleapis.com/css?family=Roboto:400i" rel="stylesheet">