Add Metafields to Invoices using Order Printer

If you are using the Shopify Order Printer app, you can add metafields to any of the available templates using the following syntax:

{{ resource.metafields.namespace.key }}

For example, to append the value of a metafield with the key "X" to the line item title in the Invoice template, you can use the following code:

      {% for line_item in order.line_items %}
      <tr>
         <td>{{ line_item.quantity }}</td>
         <td>{{ line_item.title }} ( {{ line_item.product.metafields.custom_field.X }} )
         </td>
      </tr>
      {% endfor %}
Heads Up! The approach discussed below falls outside of our Scope of Support.

For other order printing apps, the process is a bit challenging. Essentially, you must transfer the metafield values to Line Item Properties when a user adds the product to their cart. 

This process requires a developer to implement it, please reach out to a Shopify expert for assistance.