Plugin woocommerce-pdf-invoices-packing-slips.
Add this code after line 105 <dl class=”meta”> on invoice.php file
`<?php if( !empty( wc_get_order_item_meta( $item[‘item_id’], ‘_special_note’, true ) ) ) : ?>
<dt>Notes:</dt>
<dd><?php echo wc_get_order_item_meta( $item[‘item_id’], ‘_special_note’, true ); ?></dd>
<?php endif; ?>`
`
