Extract PDF Attachments C#

Introduction

Ever received a PDF packed with attachments (invoices, contracts, images) and needed to extract them all programmatically? You’re not alone—this is a common challenge for developers working with document management systems, legal tech platforms, or automated invoice processing.

In this guide, you’ll learn how to extract all attachments from a PDF using C# and GroupDocs.Watermark for .NET. While the library’s name suggests it’s just for watermarks, it actually includes powerful features for extracting embedded files from PDFs—and it does it remarkably well.

Whether you’re building an automated document processing pipeline or just need to pull out a few files, this tutorial will walk you through the entire process with clear explanations and practical tips. Let’s get those attachments out!

Why Extract PDF Attachments Programmatically?

Before we dive into the code, let’s talk about why you’d want to do this in the first place. Here are some real-world scenarios where PDF attachment extraction becomes invaluable:

  • Invoice Processing: Automatically extract supporting documents (receipts, delivery notes) attached to invoice PDFs
  • Legal Document Management: Pull out exhibits and evidence files attached to legal briefs
  • Email Archiving: Extract documents that were attached to emails saved as PDFs
  • Compliance & Auditing: Batch extract attachments for regulatory review or archival purposes
  • Workflow Automation: Feed extracted files into downstream processing systems

The beauty of doing this programmatically (versus manually) is that you can process hundreds or thousands of PDFs in minutes, not days.

Prerequisites

Before we get our hands dirty with code, here’s what you’ll need:

  1. .NET Development Environment: Visual Studio 2019+ (or your preferred IDE) with .NET Core 3.1 or .NET 5+
  2. GroupDocs.Watermark for .NET: The star of our show—download the latest version from here
  3. Basic C# Knowledge: You don’t need to be an expert, but familiarity with classes, methods, and file I/O will help
  4. Sample PDF with Attachments: Create or find a test PDF that actually has files attached to it (many PDFs don’t, so make sure yours does!)

Pro Tip: If you don’t have a PDF with attachments handy, you can create one in Adobe Acrobat by going to Tools > Edit PDF > More > Attach File.

Import Namespaces

First, let’s bring in the namespaces we’ll need. Think of these as the toolboxes that contain all the classes and methods we’ll be using:

using System;
using System.IO;
using GroupDocs.Watermark.Contents.Pdf;
using GroupDocs.Watermark.Options.Pdf;

What these do:

  • System and System.IO: Handle basic file operations and console output
  • GroupDocs.Watermark.Contents.Pdf: Gives us access to PDF-specific content (like attachments)
  • GroupDocs.Watermark.Options.Pdf: Provides options for loading and processing PDFs

Step 1: Set Up Your Project

Let’s start with a clean slate and get your project configured properly.

Create a New Project

  1. Fire up Visual Studio
  2. Click “Create a new project”
  3. Select “Console App (.NET Core)” or “.NET Framework” (either works fine)
  4. Give it a meaningful name like “PdfAttachmentExtractor”
  5. Click “Create” and let Visual Studio do its thing

Add GroupDocs.Watermark for .NET

Now we need to add the GroupDocs library to your project:

  1. Right-click on your project in Solution Explorer
  2. Select “Manage NuGet Packages”
  3. Click the “Browse” tab
  4. Search for “GroupDocs.Watermark”
  5. Click “Install” on the latest version

Note: The NuGet package manager will automatically handle all dependencies, so you don’t need to worry about anything else.

Step 2: Define Your File Paths

Before we can extract anything, we need to tell our program where to find the PDF and where to save the extracted attachments.

In your Program.cs file, add this code inside your Main method:

string documentPath = "Your Document Path";
string outputDirectory = "Your Document Directory";
string outputFileName = Path.Combine(outputDirectory, Path.GetFileName(documentPath));

What’s happening here:

  • documentPath: The full path to your PDF file (e.g., “C:\Documents\invoice.pdf”)
  • outputDirectory: The folder where extracted attachments will be saved
  • outputFileName: Combined path for output (though we mainly use outputDirectory for attachments)

Real example:

string documentPath = @"C:\PDFs\ContractWithAttachments.pdf";
string outputDirectory = @"C:\ExtractedFiles\";

Important: Make sure the output directory exists, or create it programmatically with Directory.CreateDirectory(outputDirectory) before saving files.

Step 3: Load Your PDF Document

Now comes the fun part—loading your PDF into memory so we can work with it. GroupDocs.Watermark makes this surprisingly straightforward.

Create Load Options

First, we’ll create load options specifically for PDFs:

var loadOptions = new PdfLoadOptions();

What this does: This tells GroupDocs that we’re working with a PDF document. The library supports multiple formats (Word, Excel, etc.), so these options ensure the PDF is parsed correctly.

Initialize the Watermarker

Next, we’ll use the Watermarker class to load our document:

using (Watermarker watermarker = new Watermarker(documentPath, loadOptions))
{
    // Your extraction code will go here
}

Why “Watermarker” for extraction? Good question! Despite its name, the Watermarker class is actually the main entry point for interacting with any document in GroupDocs—watermarks, content extraction, metadata, you name it. Think of it as a Swiss Army knife for document manipulation.

The using statement: This ensures that the document is properly closed and resources are freed up when we’re done, even if something goes wrong. Always use this pattern when working with file streams.

Step 4: Extract the Attachments (The Main Event!)

Here’s where the magic happens. We’ll access the PDF content, loop through all attachments, and save them to disk.

Get PDF Content

Inside your using block, access the PDF’s content structure:

PdfContent pdfContent = watermarker.GetContent<PdfContent>();

What this does: This line casts the generic document content into a PDF-specific object, which gives us access to PDF-only features like attachments, pages, and annotations.

Loop Through Attachments and Save Them

Now for the grand finale—extracting each attachment:

foreach (PdfAttachment attachment in pdfContent.Attachments)
{
    Console.WriteLine("Name: {0}", attachment.Name);
    Console.WriteLine("Description: {0}", attachment.Description);
    Console.WriteLine("File type: {0}", attachment.GetDocumentInfo().FileType);
    
    // Save the attached file to disk
    File.WriteAllBytes(Path.Combine(outputDirectory, attachment.Name), attachment.Content);
}

Breaking this down:

  1. We loop through pdfContent.Attachments (a collection of all embedded files)
  2. For each attachment, we print its name, description, and file type to the console (helpful for debugging)
  3. attachment.Content contains the actual file bytes
  4. File.WriteAllBytes() writes those bytes to a new file in your output directory

Pro Tip: The attachment.Name property gives you the original filename, which is perfect for most cases. However, if you’re worried about filename conflicts (e.g., multiple attachments named “invoice.pdf”), consider adding a timestamp or unique identifier to each filename.

Common Use Cases in the Wild

Let’s look at some practical scenarios where you’d use this extraction technique:

1. Automated Invoice Processing

Your accounting system receives PDFs with supporting documents attached. Extract them all automatically and route each file type to the appropriate processing queue.

Extract all exhibits from hundreds of legal briefs during discovery. Sort by file type and index for searchability.

3. Archive Migration

Moving from an old document management system? Extract all attachments from archived PDFs and re-import them into your new system with proper metadata.

4. Compliance Audits

Extract all attachments from quarterly reports for audit trails and regulatory compliance verification.

Troubleshooting Common Issues

Even with great code, things can go wrong. Here are solutions to common problems:

Issue 1: “File Not Found” Exception

Symptom: Program crashes when trying to load the PDF Solution: Double-check your file path. Use File.Exists(documentPath) to verify before loading:

if (!File.Exists(documentPath))
{
    Console.WriteLine("Error: PDF file not found!");
    return;
}

Issue 2: No Attachments Found (But You Know They’re There)

Symptom: pdfContent.Attachments is empty Possible Causes:

  • The PDF doesn’t actually have attachments (check manually in Adobe Acrobat)
  • The PDF is corrupted or malformed
  • Attachments are embedded as annotations, not true PDF attachments (different feature)

Solution: Verify the PDF structure and ensure attachments are properly embedded, not just linked.

Issue 3: “Access Denied” When Saving Files

Symptom: Exception thrown when calling File.WriteAllBytes() Solution: Ensure your output directory exists and you have write permissions:

if (!Directory.Exists(outputDirectory))
{
    Directory.CreateDirectory(outputDirectory);
}

Issue 4: Memory Issues with Large PDFs

Symptom: Out of memory exceptions when processing large files Solution: Process attachments one at a time and dispose of content immediately. The using statement already helps, but for very large files, consider processing in batches.

Best Practices for Production Environments

If you’re building this into a production system, keep these tips in mind:

1. Handle File Name Collisions

Multiple attachments might have the same name. Add unique identifiers:

string safeName = $"{Path.GetFileNameWithoutExtension(attachment.Name)}_{Guid.NewGuid()}{Path.GetExtension(attachment.Name)}";

2. Validate File Types

Before saving, check if the file type is expected/allowed:

var allowedTypes = new[] { ".pdf", ".docx", ".xlsx", ".jpg", ".png" };
string extension = Path.GetExtension(attachment.Name).ToLower();
if (!allowedTypes.Contains(extension))
{
    Console.WriteLine($"Skipping disallowed file type: {attachment.Name}");
    continue;
}

3. Log Everything

Add comprehensive logging for debugging and audit trails:

Console.WriteLine($"[{DateTime.Now}] Extracted: {attachment.Name} ({attachment.Content.Length} bytes)");

4. Implement Error Handling

Wrap your extraction code in try-catch blocks:

try
{
    File.WriteAllBytes(outputPath, attachment.Content);
}
catch (Exception ex)
{
    Console.WriteLine($"Failed to save {attachment.Name}: {ex.Message}");
}

5. Consider Async Processing

For high-volume scenarios, use async methods to avoid blocking:

await File.WriteAllBytesAsync(outputPath, attachment.Content);

Performance Considerations

When working with PDF attachment extraction at scale, keep these performance tips in mind:

  • Memory Usage: Each PDF is loaded entirely into memory. For large PDFs (100MB+), consider processing in batches
  • Disk I/O: Writing files to disk is the slowest part. Consider using an SSD for your output directory
  • Parallel Processing: If extracting from multiple PDFs, use Parallel.ForEach or Tasks to process them concurrently
  • Streaming: For extremely large attachments, consider streaming the content instead of loading it all at once

Frequently Asked Questions

Can I extract attachments from password-protected PDFs?

Yes! You’ll need to provide the password when loading the document. Use the PdfLoadOptions to set the password:

var loadOptions = new PdfLoadOptions { Password = "yourPassword" };

Does this work with all PDF versions?

GroupDocs.Watermark supports PDF versions 1.2 through 2.0, which covers virtually all PDFs you’ll encounter in the wild.

What file types can be extracted?

Any file type that can be embedded in a PDF—Word docs, Excel sheets, images, other PDFs, even executables (though be cautious with those!).

How do I know if a PDF has attachments before processing it?

Check the Attachments collection count:

if (pdfContent.Attachments.Count > 0)
{
    Console.WriteLine($"Found {pdfContent.Attachments.Count} attachments");
}

Can I extract just specific attachments by name or type?

Absolutely! Just add a condition inside your loop:

if (attachment.Name.EndsWith(".pdf") || attachment.Name.Contains("invoice"))
{
    // Extract only matching files
}

Is there a file size limit for extraction?

No hard limit from GroupDocs itself, but you’re constrained by available system memory. Very large attachments (1GB+) might require special handling.

Can I modify attachments and re-embed them?

Not directly through the extraction API, but you could extract, modify, and then use GroupDocs to create a new PDF with updated attachments.

Conclusion

And there you have it—a complete guide to extracting PDF attachments using C# and GroupDocs.Watermark for .NET! You’ve learned how to:

  • Set up your project and load PDFs programmatically
  • Extract all attachments with just a few lines of code
  • Handle common issues and edge cases
  • Implement best practices for production systems
  • Optimize performance for large-scale processing

The beauty of this approach is its simplicity—once you’ve got the basic pattern down, you can adapt it to all sorts of document processing workflows. Whether you’re building an invoice processing system, a legal document manager, or just need to extract some files from a PDF, you now have the tools and knowledge to get it done.

Remember, GroupDocs.Watermark offers way more than just attachment extraction (watermarking, metadata management, content search, and more), so don’t be afraid to explore the library further as your needs grow.

Now go forth and extract those attachments with confidence! And if you run into any issues, the troubleshooting section has your back.

FAQ’s

What is GroupDocs.Watermark for .NET?

GroupDocs.Watermark for .NET is a comprehensive library for adding, removing, and managing watermarks in various document formats, including PDFs. It also offers powerful capabilities for extracting embedded files and manipulating document content.

Can I extract other types of files embedded in a PDF?

Yes! GroupDocs.Watermark for .NET allows you to extract any type of file embedded in a PDF as an attachment—not just specific formats. If it’s attached, you can extract it.

Is there a free trial available?

Absolutely! You can download a free trial of GroupDocs.Watermark for .NET from here to test it out before committing to a license.

How can I get support if I encounter issues?

You can get support by visiting the GroupDocs.Watermark support forum, where community members and GroupDocs staff can help troubleshoot issues.

Do I need a license to use GroupDocs.Watermark for .NET?

Yes, you need a license to use the library in production environments. You can purchase a license here or obtain a temporary license here for evaluation purposes.