pdf-generation

PDF Generation

Puppeteer HTML-to-PDF (recommended for complex layouts)

import puppeteer from 'puppeteer';

async function generatePdf(html: string): Promise<Buffer> {
  const browser = await puppeteer.launch({ headless: true });
  const page = await browser.newPage();
  await page.setContent(html, { waitUntil: 'networkidle0' });

  const pdf = await page.pdf({
    format: 'A4',
    margin: { top: '20mm', bottom: '20mm', left: '15mm', right: '15mm' },
    printBackground: true,
  });

  await browser.close();
  return Buffer.from(pdf);
}

// Express endpoint
app.get('/api/invoice/:id/pdf', async (req, res) => {
  const invoice = await getInvoice(req.params.id);
  const html = renderInvoiceHtml(invoice);
  const pdf = await generatePdf(html);
  res.contentType('application/pdf');
  res.setHeader('Content-Disposition', `attachment; filename="invoice-${invoice.number}.pdf"`);
  res.send(pdf);
});

PDFKit (Node.js — programmatic)

import PDFDocument from 'pdfkit';

function createInvoicePdf(invoice: Invoice): Promise<Buffer> {
  return new Promise((resolve) => {
    const doc = new PDFDocument({ size: 'A4', margin: 50 });
    const chunks: Buffer[] = [];
    doc.on('data', (chunk) => chunks.push(chunk));
    doc.on('end', () => resolve(Buffer.concat(chunks)));

    // Header
    doc.fontSize(20).text('INVOICE', { align: 'right' });
    doc.fontSize(10).text(`#${invoice.number}`, { align: 'right' });
    doc.moveDown();

    // Table
    doc.fontSize(12).text('Item', 50, doc.y);
    doc.text('Amount', 400, doc.y - 12, { width: 100, align: 'right' });
    doc.moveTo(50, doc.y).lineTo(550, doc.y).stroke();

    for (const item of invoice.items) {
      doc.text(item.description, 50, doc.y + 5);
      doc.text(`$${item.amount.toFixed(2)}`, 400, doc.y - 12, { width: 100, align: 'right' });
    }

    doc.end();
  });
}

@react-pdf/renderer (React components to PDF)

import { Document, Page, Text, View, StyleSheet, renderToBuffer } from '@react-pdf/renderer';

const styles = StyleSheet.create({
  page: { padding: 30 },
  title: { fontSize: 24, marginBottom: 20 },
  row: { flexDirection: 'row', justifyContent: 'space-between', marginBottom: 5 },
});

function InvoicePdf({ invoice }: { invoice: Invoice }) {
  return (
    <Document>
      <Page size="A4" style={styles.page}>
        <Text style={styles.title}>Invoice #{invoice.number}</Text>
        {invoice.items.map((item) => (
          <View key={item.id} style={styles.row}>
            <Text>{item.description}</Text>
            <Text>${item.amount.toFixed(2)}</Text>
          </View>
        ))}
      </Page>
    </Document>
  );
}

// Server-side render
const buffer = await renderToBuffer(<InvoicePdf invoice={invoice} />);

Python (ReportLab)

from reportlab.lib.pagesizes import A4
from reportlab.platypus import SimpleDocTemplate, Table, Paragraph
from reportlab.lib.styles import getSampleStyleSheet

def generate_invoice_pdf(invoice: dict, output_path: str):
    doc = SimpleDocTemplate(output_path, pagesize=A4)
    styles = getSampleStyleSheet()
    elements = []

    elements.append(Paragraph(f"Invoice #{invoice['number']}", styles['Title']))

    data = [['Item', 'Amount']]
    for item in invoice['items']:
        data.append([item['description'], f"${item['amount']:.2f}"])

    table = Table(data, colWidths=[350, 100])
    elements.append(table)
    doc.build(elements)

Anti-Patterns

Anti-Pattern	Fix
New browser per PDF request	Reuse browser instance, create new pages
No timeout on PDF generation	Set page.setDefaultTimeout() and abort
Generating PDFs synchronously in request	Use background job queue
Inline CSS in HTML templates	Use embedded <style> or printBackground: true
No memory cleanup	Close pages after use, limit concurrent generations

Production Checklist

• Browser instance pooling (Puppeteer/Playwright)
• PDF generation in background queue
• Memory limits and timeouts configured
• Generated PDFs stored in object storage (S3)
• Content-Disposition header for downloads
• PDF/A compliance if archiving required