Additional filters have been introduced with version 1.7.1. and up. These can be used to add addtional HTML into the data. You need to return a HTML inside your add_filters option:
// Category HTML
apply_filters( 'woocommerce_pdf_catalog_category_html', $categoryTemplate->get_template($categoryLayout), $category_id);
// Product HTML
apply_filters('woocommerce_pdf_catalog_single_product_html', $html, $this->data->ID)
// All Product Data
apply_filters('woocommerce_pdf_catalog_product_data', $this->data);
// Product Information Filters - return $HTML
apply_filters('woocommerce_pdf_catalog_before_product_information', '', $this->data->ID);
apply_filters('woocommerce_pdf_catalog_before_product_information_start', '', $this->data->ID);
apply_filters('woocommerce_pdf_catalog_before_product_information_read_more', '', $this->data->ID);
apply_filters('woocommerce_pdf_catalog_before_product_information_categories', '', $this->data->ID);
apply_filters('woocommerce_pdf_catalog_before_product_information_end', '', $this->data->ID);
apply_filters('woocommerce_pdf_catalog_after_product_information', '', $this->data->ID);