Generating PDF Invoices from HTML Templates

HTML to PDF: The Use Cases

• Invoices and receipts — generate from an invoice template with order data
• Reports — render a data table as a PDF attachment
• Certificates — personalised PDFs from an HTML template
• Confirmations — booking and contract summaries

Using HTML as the source format means you can use CSS for styling, apply the same brand design as your web UI, and manage layout with Flexbox and Grid.

API Usage

curl -X POST https://api.toolkitapi.io/v1/pdf/html-to-pdf \
  -H "X-API-Key: $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "html": "<h1>Invoice #1042</h1><p>Amount: $299.00</p>",
    "options": {
      "paper_size": "A4",
      "margin": "20mm",
      "orientation": "portrait"
    }
  }' --output invoice.pdf

Injecting Data into Templates

Use Jinja2 or your preferred templating engine server-side before sending to the API:

from jinja2 import Template

template = Template(Path("templates/invoice.html").read_text())
html = template.render(
    order_id="ORD-1042",
    line_items=order.items,
    total=order.total,
    customer=customer,
)

resp = httpx.post(
    "https://api.toolkitapi.io/v1/pdf/html-to-pdf",
    headers={"X-API-Key": API_KEY},
    json={"html": html, "options": {"paper_size": "A4"}},
)
Path(f"invoices/{order.id}.pdf").write_bytes(resp.content)

CSS Tips for PDF

• Use @page rules to control margins and page size
• Avoid vh/vw units — they don't translate to paper
• Use page-break-before: always to force page breaks
• Web fonts work, but embed them with @font-face for offline rendering

Header and Footer

Pass header_html and footer_html to add repeating page headers and footers:

{
  "header_html": "<div style='font-size:9px;text-align:right'>CONFIDENTIAL</div>",
  "footer_html": "<div style='font-size:9px'>Page <span class='pageNumber'></span> of <span class='totalPages'></span></div>"
}