First Invoice With Rendro

Render a deterministic invoice PDF from Elixir data, preview it inline, and download the same bytes.

Setup

rendro_dep =
  if System.get_env("RENDRO_LIVEBOOK_LOCAL") == "1" do
    {:rendro, path: System.get_env("RENDRO_LIVEBOOK_PATH") || File.cwd!()}
  else
    {:rendro, "~> 1.0"}
  end

Mix.install([
  rendro_dep,
  {:jason, "~> 1.4"},
  {:jsv, "~> 0.19"},
  {:yaml_elixir, ">= 2.11.0 and < 3.0.0"},
  {:kino, "~> 0.16"}
])

Invoice Data

invoice = %{
  id: "LB-2026-001",
  date: ~D[2026-06-11],
  items: [
    %{name: "Implementation Sprint", qty: 2, price: 2400},
    %{name: "Support Retainer", qty: 1, price: 800},
    %{name: "Validation Report", qty: 1, price: 450}
  ]
}

Render

doc = Rendro.Recipes.Invoice.document(invoice)
{:ok, pdf} = Rendro.render(doc, deterministic: true)

if binary_part(pdf, 0, 5) != "%PDF-" do
  raise "expected Rendro to render a PDF"
end

sha256 = :crypto.hash(:sha256, pdf) |> Base.encode16(case: :lower)

%{
  bytes: byte_size(pdf),
  sha256: sha256
}

Preview

encoded = Base.encode64(pdf)

Kino.HTML.new("""
<iframe
  title="Rendro invoice PDF preview"
  src="data:application/pdf;base64,#{encoded}"
  style="width: 100%; height: 640px; border: 1px solid #d1d5db;">
</iframe>
""")

Download

Kino.Download.new(fn -> pdf end, filename: "rendro-invoice.pdf")

Phoenix Handoff

The controller shape is intentionally schematic and is not executed in this notebook.

defmodule MyAppWeb.InvoiceController do
  use MyAppWeb, :controller

  def show(conn, %{"id" => id}) do
    invoice = Billing.get_invoice!(id)
    doc = Rendro.Recipes.Invoice.document(invoice)
    {:ok, pdf} = Rendro.render(doc, deterministic: true)

    conn
    |> put_resp_content_type("application/pdf")
    |> put_resp_header("content-disposition", "inline; filename=invoice-#{id}.pdf")
    |> send_resp(200, pdf)
  end
end

Next

• Recipes guide: guides/recipes.md
• Comparison guide: guides/comparison.md
• Self-rendered manual: assets/rendro/manual.pdf