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How to convert HTML to PDF using iTextSharp

Marcelo | Founder

Oct 23, 2024

Introducing iTextSharp: A Robust .NET PDF Library

iTextSharp is a robust PDF library for .NET, making it an excellent tool for generating PDF reports in SaaS applications, whether for invoices, summaries, or detailed documents. In this article, we’ll explore how to convert HTML to PDF using iTextSharp. By leveraging C# and this library, you’ll be able to integrate PDF generation seamlessly into your projects.

You can check out the full documentation here.

Comparison Between iTextSharp and Other C# PDF Libraries

When selecting a PDF library, it’s crucial to consider factors like functionality, ease of use, and licensing. Here’s how iTextSharp compares to other popular options:

Download comparison between pdf libraries using nuget trends

• iTextSharp: The most popular pdf library for C#. A feature-rich library supporting advanced PDF creation and manipulation. Ideal for complex tasks but requires attention to licensing for commercial use.

• PdfSharp: An open-source library suitable for basic PDF tasks. While it excels in creating PDFs from scratch, it lacks native support for HTML to PDF conversion without additional extensions.

• QuestPDF: A modern, open-source library offering a fluent API for building PDFs using C#. It excels at programmatic PDF generation but doesn’t natively support HTML to PDF conversion.

• PuppeteerSharp and Playwright: Headless browser tools that render HTML to PDF by simulating a browser environment. They handle modern HTML/CSS well but can introduce unnecessary overhead for simple tasks.

iTextSharp strikes a balance between functionality and performance, making it a solid choice for converting HTML to PDF in a .NET environment.

Guide to generate pdf from html using C# iTextSharp

Setting Up iTextSharp in Your C# Project

Before diving into code, you’ll need to set up iTextSharp in your project.

Installing iTextSharp via NuGet in a .NET Environment

Use the NuGet Package Manager to install iTextSharp:

Install-Package iTextSharp -Version 5

Or via the Package Manager Console:

PM> Install-Package iTextSharp -Version 5

Ensure that your project targets a compatible .NET framework version.

Preparing Your Project for HTML to PDF Conversion

Add the necessary namespaces in your C# files:

using iTextSharp.text;
using iTextSharp.text.pdf;
using iTextSharp.tool.xml

Verify that all dependencies are correctly referenced to avoid runtime issues.

Implementing HTML to PDF Conversion with iTextSharp

Let’s walk through creating a complete invoice in HTML/CSS and converting it to PDF.

Start by designing your invoice template in HTML:

<!DOCTYPE html>
<html>
<head>
    <style>
        body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; }
        .invoice-box {
            max-width: 800px;
            margin: auto;
            padding: 30px;
            border: 1px solid #eee;
        }
        .invoice-header { text-align: center; margin-bottom: 50px; }
        .invoice-details { width: 100%; border-collapse: collapse; }
        .invoice-details th, .invoice-details td {
            border: 1px solid #ddd;
            padding: 8px;
        }
        .invoice-details th { background-color: #f2f2f2; }
    </style>
</head>
<body>
    <div class="invoice-box">
        <div class="invoice-header">
            <h1>{{ CompanyName }}</h1>
            <p>{{ Address }}</p>
        </div>
        <table class="invoice-details">
            <tr>
                <th>Description</th>
                <th>Quantity</th>
                <th>Price</th>
                <th>Total</th>
            </tr>
            {% for item in Items %}
            <tr>
                <td>{{ item.Description }}</td>
                <td>{{ item.Quantity }}</td>
                <td>${{ item.Price }}</td>
                <td>${{ item.Total }}</td>
            </tr>
            {% endfor %}
            <tr>
                <td colspan="3" style="text-align:right;">Subtotal</td>
                <td>${{ Subtotal }}</td>
            </tr>
            <tr>
                <td colspan="3" style="text-align:right;">Tax</td>
                <td>${{ Tax }}</td>
            </tr>
            <tr>
                <td colspan="3" style="text-align:right;">Total</td>
                <td>${{ Total }}</td>
            </tr>
        </table>
    </div>
</body>
</html>

Save this HTML content as invoice_template.html.

Using Template Engines for Dynamic HTML Generation

To generate dynamic invoices populated with data, integrate a template engine like Razor or Scriban. This allows you to inject variables and loop over data structures.

Example with Scriban:

using Scriban;
string templateText = File.ReadAllText("invoice_template.html");
var template = Template.Parse(templateText);
var model = new {
    CompanyName = "Your Company",
    Address = "1234 Street, City, Country",
    Items = new[] {
        new { Description = "Product A", Quantity = 2, Price = 50, Total = 100 },
        new { Description = "Product B", Quantity = 1, Price = 75, Total = 75 }
    },
    Subtotal = 175,
    Tax = 17.5,
    Total = 192.5
};
string htmlContent = template.Render(model

This approach enables you to create personalized invoices by passing different data models.

Writing C# Code to Convert HTML to PDF

Now, let’s write the C# code to convert the HTML content into a PDF document:

using System;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;
using iTextSharp.tool.xml;
namespace PdfGenerator
{
    class Program
    {
        static void Main(string[] args)
        {
            string htmlContent = /* Your dynamic HTML content from the template engine */;
            using (FileStream stream = new FileStream("invoice.pdf", FileMode.Create))
            {
                Document pdfDoc = new Document(PageSize.A4, 25, 25, 30, 30);
                PdfWriter writer = PdfWriter.GetInstance(pdfDoc, stream);
                pdfDoc.Open();
                using (StringReader sr = new StringReader(htmlContent))
                {
                    XMLWorkerHelper.GetInstance().ParseXHtml(writer, pdfDoc, sr);
                }
                pdfDoc.Close();
                writer.Close();
            }
            Console.WriteLine("PDF generation completed successfully."

Troubleshooting Common Issues

• Missing Styles: If styles aren’t applying, ensure that your CSS is inline or embedded in the HTML.

• Encoding Problems: Specify the correct encoding if you encounter character issues.

• Images Not Displaying: Use absolute paths or embed images as base64 strings.

Integrating iTextSharp with Other PDF APIs

For enhanced functionality, you can integrate iTextSharp with other libraries:

• PdfiumViewer: For rendering PDFs within your application.

• Aspose.PDF: Offers additional features like form fields and annotations.

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

For SaaS platforms, automating PDF generation at scale might require offloading the heavy lifting to a PDF API. By integrating APIs like pdforge you can handle high-volume PDF generation, complex formatting, and post-processing, all from a single backend call.

Implementation Example in C#:

using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
namespace PdfApiIntegration
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var client = new HttpClient();
            client.DefaultRequestHeaders.Add("Authorization", "Bearer your-api-key");
            var requestBody = new
            {
                templateId = "your-template",
                data = new { html = "your-html" }
            };
            var content = new StringContent(
                Newtonsoft.Json.JsonConvert.SerializeObject(requestBody),
                Encoding.UTF8,
                "application/json"
            );
            var response = await client.PostAsync("https://api.pdforge.com/v1/pdf/sync", content);
            if (response.IsSuccessStatusCode)
            {
                var pdfBytes = await response.Content.ReadAsByteArrayAsync();
                File.WriteAllBytes("invoice.pdf", pdfBytes);
                Console.WriteLine("PDF generated using PDFForge API.");
            }
            else
            {
                Console.WriteLine("Error generating PDF: " + response.ReasonPhrase

This code sends a POST request to the pdforge API, receives the generated PDF, and saves it locally.

Conclusion

iTextSharp is a formidable tool for converting HTML to PDF within the .NET ecosystem. It’s well-suited for developers comfortable with C# who require direct control over PDF generation. However, for projects where licensing is a concern or advanced HTML/CSS rendering is needed, alternatives like PuppeteerSharp or Playwright might be preferable.

If your needs are basic PDF creation without HTML conversion, PdfSharp is a lightweight option. For large-scale PDF generation or minimizing maintenance overhead, third-party PDF APIs like pdforge offer scalable and feature-rich solutions.