PDF to Fillable PDF C#

Advanced C# SDK Techniques

Take your ConvertAPI C# integrations to the next level with advanced techniques for real-world, production-grade document conversion workflows.

These advanced patterns help you build robust, scalable, and efficient PDF to Fillable PDF pipelines in your .NET applications while maintaining flexibility and control over your document workflows.

Each example is a complete Program.cs for a new console app (dotnet new console) with the ConvertApi package added. It reads your API Token from the CONVERTAPI_TOKEN environment variable, so the token stays out of your source code: run export CONVERTAPI_TOKEN="your_api_token" on macOS and Linux, or setx CONVERTAPI_TOKEN "your_api_token" on Windows and then open a new terminal.

Convert a Remote PDF File

The following C# example demonstrates how to convert a PDF file hosted online (accessible via a public URL) directly to FILLABLE using ConvertAPI. This is useful when your documents are already stored on cloud storage (S3, Azure Blob, etc.) and you want to convert them without downloading locally first.

In this example:

• No local download needed before conversion.
• The PDF file is fetched from the provided URL.
• ConvertAPI converts it to FILLABLE and saves it to a temporary folder on your server or local machine.
• Ideal for server-side processing pipelines and automated workflows.

using ConvertApiDotNet;

var convertApi = new ConvertApi(Environment.GetEnvironmentVariable("CONVERTAPI_TOKEN"));
var sourceFile = new Uri("https://cdn.convertapi.com/public/files/demo.pdf");

Console.WriteLine($"Converting online {sourceFile} document to FILLABLE...");

var result = await convertApi.ConvertAsync("pdf", "fillable", new ConvertApiFileParam(sourceFile));
var outputFile = result.Files[0];
var fileInfo = await outputFile.SaveFileAsync(Path.Combine(Path.GetTempPath(), outputFile.FileName));

Console.WriteLine("The FILLABLE result saved to " + fileInfo);

Convert a PDF File Stream to FILLABLE and Receive a File Stream

This C# example demonstrates how to convert a PDF file provided as a stream directly to FILLABLE using ConvertAPI and receive the converted FILLABLE as a stream without writing to disk. This is ideal for in-memory processing in ASP.NET APIs, serverless functions, or pipeline services where you need to handle documents securely and efficiently.

In this example:

• You open my_file.pdf as a file stream (inputStream) and pass it to ConvertAPI with a filename hint. Any readable stream works the same way, for example a file uploaded to your ASP.NET API.
• ConvertAPI converts the document to FILLABLE without writing intermediate files to your disk.
• The converted FILLABLE is returned as a stream (outputStream) for direct processing, returning to clients, or further manipulation in your pipeline. The example copies it to a MemoryStream and prints its length.
• Ideal for secure, diskless document conversion workflows.

using ConvertApiDotNet;

var convertApi = new ConvertApi(Environment.GetEnvironmentVariable("CONVERTAPI_TOKEN"));
var inputStream = File.OpenRead("my_file.pdf");

var conversionResult = await convertApi.ConvertAsync("pdf", "fillable",
    new ConvertApiFileParam(inputStream, "my_file.pdf")
);
await using var outputStream = await conversionResult.Files.First().FileStreamAsync();

using var memory = new MemoryStream();
await outputStream.CopyToAsync(memory);
Console.WriteLine($"Received the FILLABLE as a stream: {memory.Length} bytes");

Handling Exceptions During PDF to Fillable PDF Conversion

This C# example shows how to handle exceptions when converting a PDF file to FILLABLE using ConvertAPI. By catching ConvertApiException, you can access detailed error information, making it easier to debug issues such as invalid API tokens, unsupported file formats, or conversion errors in your workflow.

In this example:

• A try-catch block safely wraps the PDF to FILLABLE conversion: it converts my_file.pdf and saves the result to the converted-files folder.
• If the API call fails, ConvertApiException provides the HTTP status code and API response details for clear diagnostics.
• This approach ensures your application can handle errors gracefully, log issues, and respond with meaningful messages to users or calling services.

using ConvertApiDotNet;
using ConvertApiDotNet.Exceptions;

try
{
    var convertApi = new ConvertApi(Environment.GetEnvironmentVariable("CONVERTAPI_TOKEN"));
    var convert = await convertApi.ConvertAsync("pdf", "fillable",
        new ConvertApiFileParam("my_file.pdf"));
    await convert.SaveFilesAsync("converted-files");
}
//Catch exceptions and write details
catch (ConvertApiException e)
{
    Console.WriteLine("Status Code: " + e.StatusCode);
    Console.WriteLine("Response: " + e.Response);
}