Спасибо большое, все четко заработало (добавив везде .$url в строки).
В catalog/controller/product/category.php после строки:
$this->data['pagination'] = $pagination->render();
добавил:
$this->document->addLink($this->url->link('product/category', 'path=' . $category_info['category_id'].$url, true), 'canonical');
if ($page > 1) {
if ($page == 2) {
$this->document->addLink($this->url->link('product/category', 'path=' . $category_info['category_id'].$url, true), 'prev');
} else {
$this->document->addLink($this->url->link('product/category', 'path=' . $category_info['category_id'].$url . '&page='. ($page - 1), true), 'prev');
}
if ($limit && ceil($product_total / $limit) > $page) {
$this->document->addLink($this->url->link('product/category', 'path=' . $category_info['category_id'].$url . '&page='. ($page + 1), true), 'next');
}
}
И в файле system/library/document.php заменил:
$this->links[md5($href)] = array(
На:
$this->links[md5($href . $rel)] = array(