This guideline gives information about how to add "Download" button for Draft Order invoice to Shopify's invoice email.
Step 1:
- Similar to the ORDER invoice, the DRAFT ORDER INVOICE can be edited and selected by going to the Frontend Download page in our app.

- Under Liquid Embedded Builder part, modify the buttons as you wish, then click Copy to copy the code.
Step 2: In your Shopify admin page, go to Settings -> Notifications -> Draft order invoice :

Step 3: Paste the previous code onto Email Body (HTML) anywhere you want, normally right after the part that contains "Visit our store":

Then click Save to finish.