Two templates, two jobs
Packing slip vs invoice
A packing slip tells the buyer what is in the box. An invoice tells them what they owe. Slipmill prints both from JSON.
Use packing-slip when the document rides with the goods. Use invoice when you need amounts, tax-as-sent, and a total in cents.
They share brand fields. They do not share a layout. You pick the template name on each POST.
Neither document is a commercial invoice for customs.
Two locked templates. POST /v1/render with x-sm-key.