Automated PDF Invoice Generation: Build It in 10 Minutes

Every SaaS needs invoices. The question is: do you spend a week integrating wkhtmltopdf, fighting Puppeteer in Docker, or wrestling with LaTeX templates? Or do you send one API call and get a PDF back?

The HTML template approach

The fastest way to generate invoices is to design them in HTML/CSS — tools you already know — then render to PDF via API. Here's a complete example.

Step 1: Build your invoice template

<div style="max-width:700px;margin:0 auto;padding:40px;font-family:sans-serif">
  <div style="display:flex;justify-content:space-between;margin-bottom:40px">
    <div>
      <h1 style="margin:0;font-size:24px">INVOICE</h1>
      <p style="color:#666;margin:4px 0">#INV-2026-042</p>
      <p style="color:#666;margin:4px 0">April 11, 2026</p>
    </div>
    <div style="text-align:right">
      <h2 style="margin:0;font-size:18px">Your Company</h2>
      <p style="color:#666;margin:4px 0">[email protected]</p>
    </div>
  </div>

  <table style="width:100%;border-collapse:collapse;margin-bottom:30px">
    <thead>
      <tr style="border-bottom:2px solid #333">
        <th style="text-align:left;padding:8px 0">Item</th>
        <th style="text-align:right;padding:8px 0">Amount</th>
      </tr>
    </thead>
    <tbody>
      <tr style="border-bottom:1px solid #eee">
        <td style="padding:8px 0">Growth Plan — April 2026</td>
        <td style="text-align:right;padding:8px 0">$49.00</td>
      </tr>
      <tr>
        <td style="padding:8px 0;font-weight:bold">Total</td>
        <td style="text-align:right;padding:8px 0;font-weight:bold">$49.00</td>
      </tr>
    </tbody>
  </table>

  <p style="color:#666;font-size:14px">Payment received. Thank you!</p>
</div>

Step 2: Render to PDF

import requests

invoice_html = build_invoice(customer, line_items)  # your template function

resp = requests.post(
    "https://screenshotapis.org/v1/pdf",
    headers={"X-Api-Key": "sk_live_your_key"},
    json={
        "html": invoice_html,
        "format": "A4",
        "print_background": True,
    },
)

with open(f"invoice-{invoice_id}.pdf", "wb") as f:
    f.write(resp.content)

Step 3: Email it

Attach the PDF bytes to your transactional email. Works with SendGrid, Resend, Postmark, or any email provider that accepts attachments.

Why this beats the alternatives

• vs. wkhtmltopdf — wkhtmltopdf uses an ancient WebKit engine. CSS flexbox, grid, and modern fonts render incorrectly. Screenshot API uses current Chromium.
• vs. Puppeteer/Playwright — no browser to install, no Docker config, no memory management. Works in serverless functions out of the box.
• vs. LaTeX — you already know HTML/CSS. LaTeX has a learning curve and looks like it was designed in 1985 (because it was).
• vs. ReportLab/WeasyPrint — Python-only, limited CSS support, separate layout language. HTML gives you pixel-perfect control with tools you use every day.

Tips for production invoices

• Use print_background: true to include colored headers and brand elements
• Set explicit widths in your HTML — PDF rendering uses a fixed viewport
• Include your logo as a base64 data URI so it renders without external requests
• Test with A4 and Letter formats if you have international customers
• Cache the rendered PDF — an invoice only needs to be generated once