After a little bit tinkering here is the solution. I just made my own template copying everything from existing
1. plugins/woocommerce-pdf-invoices-packing-slips/templates/pdf/{your template name}/invoice.php
2. Add new table rows
<thead>
<tr>
<th class="product"><?php _e('Product', 'wpo_wcpdf'); ?></th>
<th class="quantity"><?php _e('Quantity', 'wpo_wcpdf'); ?></th>
<th class="price"><?php _e('Product price without VAT', 'wpo_wcpdf'); ?></th>
<th class="price"><?php _e('Product prices VAT', 'wpo_wcpdf'); ?></th>
<th class="price"><?php _e('Price including VAT', 'wpo_wcpdf'); ?></th>
</tr>
</thead>
3. Next find <td class=”price”><?php echo $item[‘order_price’]; ?></td> and replace it with
<td class="price"><?php echo $item['line_total']; ?></td> <!-- line total (line without VAT/TAX) -->
<td class="line-tax"><?php echo $item['line_tax']; ?></td> <!-- line tax (only VAT/TAX) -->
<td class="price"><?php echo $item['order_price']; ?></td> <!-- Price total with VAT/TAX (single line) -->
And that’s all.
Hope it helps.