It's a great extension. However, there's a conflict between addcustomtag() function and the pdf core generation.

To fix it, just open the yoo_effect.php file and, at the end, put a conditional so replace:
if ($javascript) $document->addCustomTag($javascript);
if ($lightbox) $document->addStyleSheet($plugin_base . 'lightbox/shadowbox.css');

by

if ($_GET['format'] !=pdf ){
if ($javascript) $document->addCustomTag($javascript);
if ($lightbox) $document->addStyleSheet($plugin_base . 'lightbox/shadowbox.css');
}

That's all.