In order to remove invoice information meta from the PDF invoice template, simply use below filter function as an example and add it to your themes functions.php file.

/**
 * Remove Order Number and Order Date.
 *
 * @param array         $info    Invoice info meta.
 * @param BEWPI_Invoice $invoice Invoice object.
 *
 * @return array.
 * @since 2.9.8
 *
 */
function remove_invoice_information_meta( $info, $invoice ) {
	unset( $info['order_number'] );
	unset( $info['order_date'] );

	return $info;
}

add_filter( 'wpi_invoice_information_meta', 'remove_invoice_information_meta', 10, 2 );