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PDF Generation Best Practices for Web Applications

Essential tips and best practices for implementing robust PDF generation in your web applications, from HTML optimization to error handling.

July 20, 2025

5 min read

Generating PDFs programmatically can be tricky. Poor implementation can lead to broken layouts, inconsistent rendering, and frustrated users. Here's a comprehensive guide to PDF generation best practices that will help you avoid common pitfalls.

HTML Structure Best Practices

1. Use Semantic HTML

Structure your HTML documents properly with semantic elements:

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Invoice #12345</title>
</head>
<body>
  <header>
    <!-- Company logo and details -->
  </header>
  <main>
    <!-- Document content -->
  </main>
  <footer>
    <!-- Page footer information -->
  </footer>
</body>
</html>

2. Avoid Absolute Positioning

Absolute positioning can cause elements to overlap or disappear in PDFs:

/* ❌ Avoid */
.element {
  position: absolute;
  top: 100px;
  left: 50px;
}

/* ✅ Better */
.element {
  margin-top: 2rem;
  margin-left: 1rem;
}

3. Use Flexbox and Grid Carefully

While modern PDF engines support flexbox and grid, keep layouts simple:

/* ✅ Good for PDFs */
.invoice-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
}

/* ⚠️ Complex grid might cause issues */
.complex-grid {
  display: grid;
  grid-template-areas: "header header"
                       "sidebar main"
                       "footer footer";
}

CSS Optimization

1. Inline Critical CSS

For better rendering consistency, inline your CSS:

<style>
  body { 
    font-family: Arial, sans-serif; 
    margin: 0; 
    padding: 20px; 
  }
  .invoice-table { 
    width: 100%; 
    border-collapse: collapse; 
  }
</style>

2. Use Print-Specific Styles

Take advantage of print media queries:

@media print {
  .no-print { display: none; }
  .page-break { page-break-before: always; }
  body { font-size: 12pt; }
}

3. Specify Exact Measurements

Use absolute units for predictable layouts:

/* ✅ Specific measurements */
.invoice-table {
  width: 100%;
  font-size: 11pt;
  line-height: 1.2;
}

/* ❌ Avoid viewport units */
.header {
  height: 10vh; /* May not work as expected */
}

Table Design Guidelines

Tables are common in PDFs but can be problematic. Here's how to do them right:

1. Proper Table Structure

<table class="invoice-table">
  <thead>
    <tr>
      <th>Description</th>
      <th>Quantity</th>
      <th>Price</th>
      <th>Total</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Product Name</td>
      <td>2</td>
      <td>$50.00</td>
      <td>$100.00</td>
    </tr>
  </tbody>
</table>

2. Table CSS

.invoice-table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 20px;
}

.invoice-table th,
.invoice-table td {
  padding: 8px 12px;
  border: 1px solid #ddd;
  text-align: left;
}

.invoice-table th {
  background-color: #f5f5f5;
  font-weight: bold;
}

Image Handling

1. Optimize Image Sizes

Large images can slow down PDF generation:

.logo {
  max-width: 200px;
  height: auto;
}

.product-image {
  width: 100px;
  height: 100px;
  object-fit: cover;
}

2. Use Proper Image Formats

PNG: For logos and graphics with transparency
JPEG: For photographs
SVG: For vector graphics (ensure compatibility)

3. Handle Missing Images

Always provide fallbacks:

<img src="logo.png" 
     alt="Company Logo" 
     onerror="this.style.display='none'">

Error Handling and Resilience

1. Implement Proper Error Handling

async function generatePDF(htmlContent) {
  try {
    const response = await fetch('/api/generate-pdf', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${apiKey}`
      },
      body: JSON.stringify({ html: htmlContent })
    });

    if (!response.ok) {
      throw new Error(`PDF generation failed: ${response.status}`);
    }

    return await response.arrayBuffer();
  } catch (error) {
    console.error('PDF generation error:', error);
    // Implement retry logic or fallback
    throw error;
  }
}

2. Validate HTML Before Generation

function validateHTMLForPDF(html) {
  const issues = [];
  
  // Check for common problematic elements
  if (html.includes('position: fixed')) {
    issues.push('Fixed positioning detected');
  }
  
  if (html.includes('transform:')) {
    issues.push('CSS transforms may not render correctly');
  }
  
  return issues;
}

Performance Optimization

1. Cache PDF Results

const pdfCache = new Map();

async function getCachedPDF(cacheKey, htmlContent) {
  if (pdfCache.has(cacheKey)) {
    return pdfCache.get(cacheKey);
  }
  
  const pdf = await generatePDF(htmlContent);
  pdfCache.set(cacheKey, pdf);
  
  return pdf;
}

2. Minimize API Calls

Batch multiple documents when possible:

async function generateMultiplePDFs(documents) {
  const requests = documents.map(doc => ({
    html: doc.html,
    filename: doc.filename
  }));
  
  return await fetch('/api/batch-generate', {
    method: 'POST',
    body: JSON.stringify({ documents: requests })
  });
}

Testing and Quality Assurance

1. Test Across Different Content

Short documents (1 page)
Long documents (10+ pages)
Documents with tables
Documents with images
Multi-language content

2. Automated Testing

describe('PDF Generation', () => {
  test('should generate invoice PDF', async () => {
    const html = generateInvoiceHTML(mockData);
    const pdf = await generatePDF(html);
    
    expect(pdf).toBeDefined();
    expect(pdf.byteLength).toBeGreaterThan(1000);
  });
  
  test('should handle missing images gracefully', async () => {
    const html = '<img src="missing.jpg" alt="Missing">';
    const pdf = await generatePDF(html);
    
    expect(pdf).toBeDefined();
  });
});

Monitoring and Analytics

1. Track Generation Metrics

const pdfMetrics = {
  generationTime: Date.now(),
  documentSize: html.length,
  success: false,
  errorMessage: null
};

try {
  const pdf = await generatePDF(html);
  pdfMetrics.success = true;
  pdfMetrics.pdfSize = pdf.byteLength;
} catch (error) {
  pdfMetrics.errorMessage = error.message;
} finally {
  pdfMetrics.generationTime = Date.now() - pdfMetrics.generationTime;
  
  // Send metrics to your analytics service
  analytics.track('pdf_generation', pdfMetrics);
}

Conclusion

Following these best practices will help you build robust PDF generation functionality that works reliably across different scenarios. Remember to test thoroughly and monitor your PDF generation in production.

The key is to keep your HTML and CSS simple, handle errors gracefully, and optimize for performance. With BlazePDF, many of these concerns are handled for you, but following these practices will ensure the best possible results.

Want to see these practices in action? Try BlazePDF's sandbox and experiment with different HTML structures!