Generate PDF from HTML Using PDFMake: A Developer’s Guide

Setting Up Your Environment for PDFMake and Node.js

Installing PDFMake and Node.js for Seamless Integration

To start building PDFs, ensure that you have Node.js installed. Then, integrate PDFMake into your project by installing it with npm:

npm install pdfmake --save

This command adds PDFMake to your project, allowing you to programmatically generate PDFs from within a Node.js environment. With this setup, you can begin assembling PDFs using JavaScript objects.

Setting Up Your Project Structure for HTML to PDF Conversion

To demonstrate how PDFMake can replicate an HTML document, let’s use an example of an invoice written in plain HTML and CSS:

<div class="invoice">
  <h1>Invoice #1234</h1>
  <p>Date: 2024-10-01</p>
  <p>Customer: John Doe</p>
  <table>
    <tr>
      <th>Item</th>
      <th>Quantity</th>
      <th>Price</th>
    </tr>
    <tr>
      <td>Widget A</td>
      <td>2</td>
      <td>$10</td>
    </tr>
    <tr>
      <td>Widget B</td>
      <td>5</td>
      <td>$20</td>
    </tr>
  </table>
</div>

This simple invoice file will serve as our reference for building a similar layout using PDFMake. Since PDFMake doesn't render HTML directly, we must replicate the structure programmatically.

Converting HTML to PDF with PDFMake: Step-by-Step Guide

Styling Your PDFs: How to Replicate HTML and CSS Styles Using PDFMake

Since PDFMake doesn’t convert raw HTML into PDFs, you need to define the content structure programmatically. Let’s start by replicating the invoice’s heading and text:

const docDefinition = {
  content: [
    { text: 'Invoice #1234', style: 'header' },
    { text: 'Date: 2024-10-01', margin: [0, 20, 0, 20] },
    { text: 'Customer: John Doe', margin: [0, 20, 0, 20] }
  ],
  styles: {
    header: { fontSize: 22, bold: true },
  }
};

This structure defines the header and customer details, mimicking the HTML’s layout. You can add custom fonts and styles as needed.

Using PDFMake’s Table and Layout Features for Structured Reports

Next, we’ll convert the invoice table to PDFMake’s table format. PDFMake provides a simple API for creating tables and specifying cell alignment, similar to HTML tables:

const docDefinition = {
  content: [
    { text: 'Invoice #1234', style: 'header' },
    { text: 'Date: 2024-10-01', margin: [0, 20, 0, 20] },
    { text: 'Customer: John Doe', margin: [0, 20, 0, 20] },
    {
      table: {
        body: [
          ['Item', 'Quantity', 'Price'],
          ['Widget A', '2', '$10'],
          ['Widget B', '5', '$20']
        ]
      }
    }
  ],
  styles: {
    header: { fontSize: 22, bold: true },
  }
};

Here, the body attribute defines the rows and cells of the table, effectively replicating the HTML table structure.

Adding Images, Headers, and Footers Using PDFMake’s Features

To complete the invoice, you can add a company logo or other images using base64 or a URL reference, and customize headers and footers for page numbers or branding:

const docDefinition = {
  header: 'Company Logo Here',
  footer: (currentPage, pageCount) => `Page ${currentPage} of ${pageCount}`,
  content: [
    { text: 'Invoice #1234', style: 'header' },
    { text: 'Date: 2024-10-01', margin: [0, 20, 0, 20] },
    { text: 'Customer: John Doe', margin: [0, 20, 0, 20] },
    {
      table: {
        body: [
          ['Item', 'Quantity', 'Price'],
          ['Widget A', '2', '$10'],
          ['Widget B', '5', '$20']
        ]
      }
    }
  ],
  styles: {
    header: { fontSize: 22, bold: true },
  }
};

Creating Interactive PDFs: Adding Links and Form Fields

For interactivity, PDFMake supports hyperlinks and form fields, allowing you to create more engaging documents. You can add links to your invoices for online payment options:

const docDefinition = {
  content: [
    { text: 'Invoice #1234', style: 'header' },
    { text: 'Date: 2024-10-01', margin: [0, 20, 0, 20] },
    { text: 'Customer: John Doe', margin: [0, 20, 0, 20] },
    {
      table: {
        body: [
          ['Item', 'Quantity', 'Price'],
          ['Widget A', '2', '$10'],
          ['Widget B', '5', '$20']
        ]
      }
    },
    { text: 'Pay Now', link: 'https://payment-link.com', color: 'blue', margin: [0, 20, 0, 20] }
  ]
};

Debugging and Troubleshooting Common Issues in HTML to PDF Conversions

PDFMake doesn’t parse or render HTML. This is both a benefit and a limitation—on the one hand, you have full control over how your document is structured, but on the other, you must manually map HTML content to PDFMake’s syntax. Common issues include incorrect layout rendering or broken table structures. Always ensure that your data structure matches the expected input of PDFMake’s API.

How to Use a PDF API to Automate PDF Creation at Scale

For SaaS platforms generating PDFs at scale, you may need to offload the process to a PDF API. Third-party solutions like pdforge offer robust APIs for automating bulk PDF generation. By sending the structured data to an API, you can automate PDF creation without the need to manage resources directly.

fetch('https://api.pdforge.com/v1/pdf/sync', {
  method: 'POST',
  body: JSON.stringify({ templateId: 'your-template' , data: {html:'your-html' } }),
  headers: { 'Authorization' : 'Bearer your-api-key' }
});

Conclusion

While PDFMake offers an excellent solution for generating highly customizable PDFs with fine-grained control, it’s best suited for cases where you need to build documents from structured data. For more complex layouts or when replicating entire web pages, higher-level tools like Playwright or Puppeteer are preferable due to their ability to render PDFs based on browser rendering. For large-scale PDF generation, consider using third-party PDF Generation APIs, such as pdforge, to automate the process, ensuring performance and scalability.