Using custom fields in order notifications

Custom fields are also available for orders and their associated information. An order object in Shopify contains references to the ordering customer as well as the ordered products and variants. Also, order metafields can be collected automatically.

Examples of Liquid drops to use in e.g. a Shopify notification template:

{{ order.metafields.accentuate.purchase_order_reference }}  
{{ order.customer.metafields.accentuate.nick_name }}  

{% for line in line_items %}
   {{ line.product.metafields.accentuate.tech_description }}
   {{ line.variant.metafields.accentuate.washing_instructions }}
{% endfor %}

This example only applies to Shopify's internal notification templates. If you want to use the Order Printer app, metafields will not be available, so another approach is needed - please see this article from Shopify