Follow this instructions to include the customers text into your packing slip.
Open the store settings and click on „Shipping and delivery„.

Scroll down to the packing slip section and click on „Edit„:

Copy and paste the following code above this code line: flex-line-item-quantity
Maybe your template is different and you have to try to find the correct code position.

Copy and paste this code:

            {% if line_item.properties != blank %}

               {% for line_property in line_item.properties %}

  <span class=”line-item-description-line”>

                {{ line_property.first }} : {{line_property.last}}

                </span>

{% endfor %}

            {% endif %}