Convert HTML to PDF in C# and VB.NET

Installation

To convert HTML to PDF, you need to install GemBox.Pdf.Html.Windows or GemBox.Pdf.Html.Linux NuGet library, depending on your platform:

Install-Package GemBox.Pdf.Html.Windows
Install-Package GemBox.Pdf.Html.Linux

Both libraries are part of GemBox.Pdf and don’t require additional purchases or licensing.

Basic conversion

GemBox.Pdf provides several ways to convert HTML content to PDF, depending on where the HTML originates. You can convert a local file, a web page URL, an HTML string, or any stream that contains HTML content.

Convert HTML file to PDF

Use the ConvertFileToPdfAsync method to convert a local HTML file to PDF. This approach is ideal when generating documents from templates stored on disk. GemBox.Pdf automatically resolves and downloads external resources referenced in HTML such as images or CSS stylesheets.

var document = await HtmlConverter.ConvertFileToPdfAsync("%#Invoice.html%");
document.Save("Invoice.pdf");

Dim document = Await HtmlConverter.ConvertFileToPdfAsync("%#InputFileName%")
document.Save("Invoice.pdf")

Convert URL to PDF

Use the ConvertUrlToPdfAsync method to convert a live web page directly to PDF. This is useful for archiving web content or generating reports from online dashboards.

var document = await HtmlConverter.ConvertUrlToPdfAsync("https://www.amazon.com/");
document.Save("Website.pdf");

Dim document = Await HtmlConverter.ConvertUrlToPdfAsync("https://www.amazon.com/")
document.Save("Website.pdf")

Convert HTML string to PDF

If your application dynamically generates HTML markup, you can convert it directly using the ConvertHtmlToPdfAsync method.

var document = await HtmlConverter.ConvertHtmlToPdfAsync("<p style=\"color:red;font-size:40px;text-align:center\">Hello World!</p>");
document.Save("Document.pdf");

Dim document = Await HtmlConverter.ConvertHtmlToPdfAsync("<p style=""color:red;font-size:40px;text-align:center"">Hello World!</p>")
document.Save("Document.pdf")

Convert HTML stream to PDF

To convert any stream that contains HTML to PDF, use the ConvertToPdfAsync method. The following code snippet shows how to convert FileStream to PDF:

using var fileStream = new FileStream("Invoice.html", FileMode.Open);
var document = await HtmlConverter.ConvertToPdfAsync(fileStream);
document.Save("Invoice.pdf");

Using fileStream As New FileStream("Invoice.html", FileMode.Open)
    Dim document = Await HtmlConverter.ConvertToPdfAsync(fileStream)
    document.Save("Invoice.pdf")
End Using

Advanced conversion options

You can customize the conversion using the ConversionOptions class. The following code demonstrates how to adjust the page size and margins:

var conversionOptions = new ConversionOptions()
{
    PageSize = new PdfSize(width: 500, height: 1000),
    PageMargins = new PdfPadding(left: 50, bottom: 100, right: 50, top: 100)
};
document = await HtmlConverter.ConvertFileToPdfAsync("Invoice.html", conversionOptions);

Dim conversionOptions As New ConversionOptions() With {
    .PageSize = New PdfSize(width:=500, height:=1000),
    .PageMargins = New PdfPadding(left:=50, bottom:=100, right:=50, top:=100)
}
document = Await HtmlConverter.ConvertFileToPdfAsync("Invoice.html", conversionOptions)

The conversion methods accept a CancellationToken that allows you to cancel the operation. The following code shows how to cancel the conversion after five seconds:

using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
try
{
    document = await HtmlConverter.ConvertFileToPdfAsync("Invoice.html", cts.Token);
    // Successfully completed
}
catch (OperationCanceledException)
{
    // Operation timed out
}

Using cts As New CancellationTokenSource(TimeSpan.FromSeconds(5))
    Try
        document = Await HtmlConverter.ConvertFileToPdfAsync("Invoice.html", cts.Token)
        ' Successfully completed
    Catch ex As OperationCanceledException
        ' Operation timed out
    End Try
End Using

Windows

To enable HTML to PDF conversion on Windows, install the GemBox.Pdf.Html.Windows NuGet package.

HTML to PDF conversion is supported on Windows 10 or later and Windows Server 2016 or later. No additional system dependencies are required.

The feature can be used with any supported .NET runtime, including .NET Framework, .NET, and .NET Core, and in all common application types such as ASP.NET, WPF, Windows Forms, console applications, and Windows services.

Linux

To enable HTML to PDF conversion on Linux, install the GemBox.Pdf.Html.Linux NuGet package. Chromium, which is used internally, requires additional system dependencies to be installed. You can use the following command to install all required dependencies on Debian-based distributions.

apt-get update && apt-get install -y libasound2 libatk1.0-0 libc6 libcairo2
libcups2 libdbus-1-3 libexpat1 libfontconfig1 libgcc-s1 libgconf-2-4
libgdk-pixbuf2.0-0 libglib2.0-0 libgtk-3-0 libnspr4 libpango-1.0-0 libpangocairo-1.0-0
libstdc++6 libx11-6 libx11-xcb1 libxcb1 libxcursor1 libxdamage1 libxext6 libxfixes3
libxi6 libxrandr2 libxrender1 libxss1 libxtst6 libnss3 libgbm1


Alternatively, you can use the following method that will install missing dependencies for you:

await HtmlConverter.EnsureDependenciesAsync();

Await HtmlConverter.EnsureDependenciesAsync()

Azure App Service

While GemBox.Pdf supports HTML to PDF conversion on Azure App Service, due to performance reasons the recommended approach for deploying to the cloud is using Docker containers.

As mentioned in the Linux section, HTML to PDF requires additional system packages in order to work on Linux. In the Azure App Service environment, the storage where the packages are installed is ephemeral and cleaned when the application is redeployed or restarted.

To use the HTML to PDF feature in Azure App Service, we recommend including the following code in Startup.cs or Program.cs:

await HtmlConverter.EnsureDependenciesAsync();

Await HtmlConverter.EnsureDependenciesAsync()

We additionally recommend the app to be “Always On” which prevents it from being idled out due to inactivity.

To see an example that demonstrates how to create an Azure App Service, see the dedicated article.

Azure Functions

While GemBox.Pdf supports HTML to PDF conversion on Azure Functions, due to performance reasons the recommended approach for deploying to the cloud is using Docker containers.

To use Azure functions on Linux, you need to ensure that the required dependencies are installed. You can put the following line at the start of the function:

await HtmlConverter.EnsureDependenciesAsync();

Await HtmlConverter.EnsureDependenciesAsync()

To see an example that demonstrates how to create an Azure Function, see the dedicated article.

Docker

You can convert HTML to PDF on Linux-based Docker images. As mentioned in the Linux section, HTML to PDF requires additional system packages in order to work on Linux. You can add the following line to your Dockerfile which will install all required dependencies:

RUN apt-get update && apt-get install -y --no-install-recommends libasound2 libatk1.0-0
libc6 libcairo2 libcups2 libdbus-1-3 libexpat1 libfontconfig1 libgcc-s1 libgconf-2-4
libgdk-pixbuf2.0-0 libglib2.0-0 libgtk-3-0 libnspr4 libpango-1.0-0 libpangocairo-1.0-0
libstdc++6 libx11-6 libx11-xcb1 libxcb1 libxcursor1 libxdamage1 libxext6 libxfixes3 libxi6
libxrandr2 libxrender1 libxss1 libxtst6 libnss3 libgbm1 && rm -rf /var/lib/apt/lists/*

Web application

You can use the following Dockerfile to build your web application into a Docker image:

FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build

WORKDIR /app

COPY *.csproj ./
RUN dotnet restore

COPY . ./
RUN dotnet publish -c Release -o /app/publish --no-restore

FROM mcr.microsoft.com/dotnet/aspnet:10.0

RUN apt-get update && apt-get install -y --no-install-recommends libasound2 libatk1.0-0 libc6 libcairo2 libcups2 libdbus-1-3 libexpat1 libfontconfig1 libgcc-s1 libgconf-2-4 libgdk-pixbuf2.0-0 libglib2.0-0 libgtk-3-0 libnspr4 libpango-1.0-0 libpangocairo-1.0-0 libstdc++6 libx11-6 libx11-xcb1 libxcb1 libxcursor1 libxdamage1 libxext6 libxfixes3 libxi6 libxrandr2 libxrender1 libxss1 libxtst6 libnss3 libgbm1 && rm -rf /var/lib/apt/lists/*

WORKDIR /app

COPY --from=build /app/publish .

ENTRYPOINT ["dotnet", "Web.dll"]

See our Docker example for detailed instructions that show how to use GemBox.Pdf in Docker container.

Azure function

You can use the following Dockerfile as a starting point for creating containerized function apps:

FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build

WORKDIR /app

COPY *.csproj ./
RUN dotnet restore

COPY . ./
RUN dotnet publish -c Release -o /app/publish --no-restore

FROM mcr.microsoft.com/azure-functions/dotnet-isolated:4-dotnet-isolated10.0

RUN apt-get update && apt-get install -y --no-install-recommends libasound2 libatk1.0-0 libc6 libcairo2 libcups2 libdbus-1-3 libexpat1 libfontconfig1 libgcc-s1 libgconf-2-4 libgdk-pixbuf2.0-0 libglib2.0-0 libgtk-3-0 libnspr4 libpango-1.0-0 libpangocairo-1.0-0 libstdc++6 libx11-6 libx11-xcb1 libxcb1 libxcursor1 libxdamage1 libxext6 libxfixes3 libxi6 libxrandr2 libxrender1 libxss1 libxtst6 libnss3 libgbm1 && rm -rf /var/lib/apt/lists/*

WORKDIR /home/site/wwwroot
COPY --from=build /app/publish .
ENV AzureWebJobsScriptRoot=/home/site/wwwroot \
   AzureFunctionsJobHost__Logging__Console__IsEnabled=true \
   FUNCTIONS_WORKER_RUNTIME=dotnet-isolated

See the official Microsoft article for more information about building and deploying containerized function apps.