Optimizer Plugin for Aspose.PDF
How to Compress PDFs Using Aspose.PDF Optimizer in .NET

How to Compress PDFs Using Aspose.PDF Optimizer in .NET

This article explains how to compress and optimize PDF documents—including images, file size, and layout—using Aspose.PDF Optimizer for .NET. Learn to apply lossless compression, resize or rotate pages, and automate batch optimization, all from C# code.

Real-World Problem

Large or unoptimized PDFs are slow to load, difficult to share, and can use excessive storage. Developers and businesses need efficient, automated solutions to compress files, rotate/crop pages, or prepare documents for web delivery or archiving.

Solution Overview

Aspose.PDF Optimizer for .NET streamlines PDF file compression and optimization. It allows for image compression, resizing, and rotation using simple, configurable options—ideal for both single files and large-scale batch processing.

Prerequisites

  • Visual Studio 2019 or later
  • .NET 6.0 or later
  • Aspose.PDF for .NET installed via NuGet
PM> Install-Package Aspose.PDF

Step-by-Step Implementation

Step 1: Install and Configure Aspose.PDF

Add the required namespaces:

using Aspose.Pdf.Plugins;
using System.IO;

Step 2: Compress and Optimize a PDF (Basic Compression) 

var optimizer = new Optimizer();
var opt = new OptimizeOptions();
opt.AddInput(new FileDataSource("input.pdf"));
opt.AddOutput(new FileDataSource("output_optimized.pdf"));
optimizer.Process(opt);

Step 3: Resize PDF Pages

To change page size (e.g., to standard Letter):

var optimizer = new Optimizer();
var resizeOpt = new ResizeOptions
{
    PageSize = PageSize.PageLetter
};
resizeOpt.AddInput(new FileDataSource("input.pdf"));
resizeOpt.AddOutput(new FileDataSource("output_resized.pdf"));
optimizer.Process(resizeOpt);

Step 4: Rotate PDF Pages

To rotate all pages by 180 degrees:

var optimizer = new Optimizer();
var rotateOpt = new RotateOptions
{
    Rotation = Rotation.on180
};
rotateOpt.AddInput(new FileDataSource("input.pdf"));
rotateOpt.AddOutput(new FileDataSource("output_rotated.pdf"));
optimizer.Process(rotateOpt);

Use Cases & Applications (With Code Variations)

1. Batch Compress Multiple PDFs

Automate optimization for all PDFs in a directory:

string[] pdfFiles = Directory.GetFiles(@"C:\Samples\ToOptimize", "*.pdf");
foreach (var file in pdfFiles)
{
    var optimizer = new Optimizer();
    var opt = new OptimizeOptions();
    opt.AddInput(new FileDataSource(file));
    string output = Path.Combine(@"C:\Samples\Optimized", Path.GetFileNameWithoutExtension(file) + "_optimized.pdf");
    opt.AddOutput(new FileDataSource(output));
    optimizer.Process(opt);
}

2. Resize and Compress for Web or Mobile Delivery

Combine resizing and compression for digital distribution (one step per run):

  • First, resize as shown above.
  • Then, optimize the resized output to compress images and reduce file size further.

3. Rotate Only Selected Pages (Advanced)

For rotating only specific pages, split PDFs or use additional logic with full Aspose.PDF API. The Optimizer rotates all pages by default.

4. Automate Cropping, Metadata Removal, and File Preparation

Although the API Reference covers core options, you may preprocess files (crop, remove metadata, etc.) using the main Aspose.PDF library for best results before or after optimization.

Common Challenges and Solutions

Challenge: Insufficient file size reduction Solution: Check input images—lossless compression may have limited impact if images are already optimized. Consider resizing pages for further reduction.

Challenge: Output quality loss Solution: Adjust optimization level and test with multiple sample files. Preview output for quality before mass deployment.

Challenge: Mixed content (scanned, text, images) Solution: Optimize settings per document type; run tests to balance size and legibility.

Performance and Best Practices

  • Batch process for large volumes
  • Store originals before overwrite
  • Validate final PDFs on target devices/platforms
  • Combine resizing/rotation steps for best automation

Complete Implementation Example 

using Aspose.Pdf.Plugins;
using System;
using System.IO;

class Program
{
    static void Main()
    {
        var optimizer = new Optimizer();
        var opt = new OptimizeOptions();
        opt.AddInput(new FileDataSource("input.pdf"));
        opt.AddOutput(new FileDataSource("output_optimized.pdf"));
        optimizer.Process(opt);
    }
}

Conclusion

Aspose.PDF Optimizer for .NET gives developers complete control over PDF file size, quality, and layout—enabling efficient storage, delivery, and management. Use built-in compression, resizing, and rotation in single steps or automated pipelines to streamline your document workflows.

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