Batch PDF Generation: Converting 1,000 Documents in Minutes

The challenge

You need to generate 500 invoices, 1,000 shipping labels, or 10,000 certificates. Doing this sequentially — one API call at a time — would take hours. You need parallel processing.

Using the batch API

const response = await fetch('https://pdfrelay.com/api/v1/batch', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer sk_live_...',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    items: invoices.map(inv => ({
      source: 'html',
      content: renderInvoiceHTML(inv),
      hosting: { enabled: true },
    })),
  }),
});

const { batch_id, poll_url } = await response.json();

The batch API processes up to 100 items per request. All items are processed in parallel by the worker pool. Poll the status endpoint to track progress.

Mixing types in a batch

A single batch can contain different conversion types:

{
  "items": [
    { "source": "html", "content": "<h1>Invoice</h1>..." },
    { "source": "url", "url": "https://dashboard.example.com/report" },
    { "type": "render", "template": "certificate", "data": { "name": "Jane" } },
    { "type": "compose", "parts": [
      { "template": "cover-page", "data": { "title": "Q1 Report" } },
      { "html": "<h2>Chapter 1</h2>..." }
    ]}
  ]
}

HTML, URLs, templates, and multi-part composed documents — all in one batch. Each rendered by the same Rust engine, no browser required.