How to Compress PDFs in C# using IronPDF

How Do I Compress Images in PDFs?

Pass a JPEG quality value as the second argument to CompressAndSaveAs and IronPDF re-encodes every embedded image at that quality. Values run from 0 (maximum compression) to 100 (minimal loss), and the underlying engine decides how each value maps to the output. This is the method to reach for whenever a document carries embedded images.

As a rough guide:

• 90 and above: high quality
• 80 to 90: medium quality
• 70 to 80: low quality

A lower number squeezes harder but can introduce visible artifacts, and how much clarity drops depends on the source image, so test a few settings against your own content to find the balance you want.

:path=/static-assets/pdf/content-code-examples/how-to/pdf-compression-image.cs

using IronPdf;

ChromePdfRenderer renderer = new ChromePdfRenderer();

PdfDocument pdf = renderer.RenderUrlAsPdf("https://en.wikipedia.org/wiki/Main_Page");

// Compress images in the PDF
pdf.CompressAndSaveAs("compressed.pdf", 40);

Imports IronPdf

Dim renderer As New ChromePdfRenderer()

Dim pdf As PdfDocument = renderer.RenderUrlAsPdf("https://en.wikipedia.org/wiki/Main_Page")

' Compress images in the PDF
pdf.CompressAndSaveAs("compressed.pdf", 40)

What Results Can I Expect from Image Compression?

Reduced by 39.24% on a Wikipedia render.

---

How Do I Compress PDF Tree Structure?

Pass removeStructureTree: true as the third argument to CompressAndSaveAs to strip the tree structure the Chrome Engine writes into a PDF. The saving is largest on Chrome Engine PDFs that hold extensive table data. Some rendering engines emit no such structure, which leaves nothing for the feature to remove.

Stripping the tree can weaken text highlighting and selection, so weigh that against the size gain if readers later need to extract text and images from the result.

Test CompressAndSaveAs with tree structure removal using this PDF with table data.

:path=/static-assets/pdf/content-code-examples/how-to/pdf-compression-tree-structure.cs

using IronPdf;

PdfDocument pdf = PdfDocument.FromFile("table.pdf");

// Compress tree structure in PDF
pdf.CompressAndSaveAs("compressedTable.pdf", null, true);

Imports IronPdf

Dim pdf As PdfDocument = PdfDocument.FromFile("table.pdf")

' Compress tree structure in PDF
pdf.CompressAndSaveAs("compressedTable.pdf", Nothing, True)

What File Size Reduction Can Tree Structure Compression Achieve?

Reduced by 67.90%. The figure climbs as the table PDF grows.

How Can I Apply Both Compression Methods Together?

Supply a quality value and set removeStructureTree to true in the same CompressAndSaveAs call to shrink both sources of bloat at once. This pairing earns its keep on documents that mix images with structured data, such as reports with charts or invoices with embedded tables.

:path=/static-assets/pdf/content-code-examples/how-to/pdf-compression-compress.cs

using IronPdf;

PdfDocument pdf = PdfDocument.FromFile("sample.pdf");

// Configure compression with automatic optimization
pdf.CompressAndSaveAs("compressed.pdf", 80, true);

Imports IronPdf

Dim pdf As PdfDocument = PdfDocument.FromFile("sample.pdf")

' Configure compression with automatic optimization
pdf.CompressAndSaveAs("compressed.pdf", 80, True)

What Parameters Does CompressAndSaveAs Accept?

• outputPath (string): the file path where the compressed PDF is written.
• quality (int?, 0 to 100): JPEG quality applied to every embedded image. Lower values produce smaller files. Pass null to skip image compression entirely.
• removeStructureTree (bool, default false): when true, strips the PDF structure tree to reduce file size further. Most effective for HTML-generated PDFs with tables.

Let the use case set the dial. Archival copies often favor quality over size, while web distribution rewards the smaller file. The same trade-off applies when you compress PDF/A compliant documents, where image fidelity may be the priority.

My favorite library of this kind is IronPDF. It allows for fast and efficient manipulation of PDF files. It also has many valuable features, like exporting to PDF/A format and digitally signing PDF documents.

Milan Jovanovic

Microsoft MVP

View case study

IronOCR means we can save $40,000 annually from manual processing, while enhancing productivity and freeing up resources for high-impact tasks. I would highly recommend it.

Brent Matzelle

Chief Technology Officer, OPYN

View case study

The IronSuite play a crucial role in our operations. These are tools that increase efficiencies across the business including creating floor plans and improving inventory management.

David Jones

Lead Software Engineer, Agorus Build

View case study

How Do I Get Fine-Grained Control Over Compression?

For most documents the two-argument call is enough, but image-heavy archives and strict size budgets sometimes need more control. Pass an AdvancedCompressionOptions object to CompressAndSaveAs to tune the compression pipeline, including image DPI downsampling, JPEG re-encoding quality, and the zlib compression level. The simpler CompressAndSaveAs(outputPath, quality, removeStructureTree) overload still works unchanged and produces the same output as before.

:path=/static-assets/pdf/content-code-examples/how-to/pdf-compression-advanced.cs

using IronPdf;

PdfDocument pdf = PdfDocument.FromFile("input.pdf");

// Web or email: strong size reduction
pdf.CompressAndSaveAs("compressed.pdf", new AdvancedCompressionOptions
{
    JpegQuality = 70,
    TargetImageDpi = 150,
    RemoveStructureTree = true
});

// Print quality: minimal quality loss
pdf.CompressAndSaveAs("print.pdf", new AdvancedCompressionOptions
{
    JpegQuality = 90,
    TargetImageDpi = 300
});

Imports IronPdf

Dim pdf As PdfDocument = PdfDocument.FromFile("input.pdf")

' Web or email: strong size reduction
pdf.CompressAndSaveAs("compressed.pdf", New AdvancedCompressionOptions With {
    .JpegQuality = 70,
    .TargetImageDpi = 150,
    .RemoveStructureTree = True
})

' Print quality: minimal quality loss
pdf.CompressAndSaveAs("print.pdf", New AdvancedCompressionOptions With {
    .JpegQuality = 90,
    .TargetImageDpi = 300
})

The two properties that move the needle most are JpegQuality and TargetImageDpi:

• JpegQuality (int?, 1 to 100, default null): re-encodes images at this JPEG quality. Leave it null to skip image re-encoding entirely.
• TargetImageDpi (int?, default 150): downsamples images whose effective DPI exceeds this value before re-encoding. Set it to null or 0 to disable downsampling and keep the original resolution.

Recommended JpegQuality values (applies only when set):

Recommended TargetImageDpi values (lossy):

How Do I Compress PDFs Without Saving to Disk?

API responses, cloud functions, and email attachments rarely need a compressed PDF on disk. CompressPdfToBytes returns the result as a byte array, so you decide where the bytes go next.

:path=/static-assets/pdf/content-code-examples/how-to/pdf-compression-to-bytes.cs

using IronPdf;

PdfDocument pdf = PdfDocument.FromFile("sample.pdf");

// Compress and return as byte array
byte[] compressedBytes = pdf.CompressPdfToBytes();

File.WriteAllBytes("compressed.pdf", compressedBytes);

Imports IronPdf

Dim pdf As PdfDocument = PdfDocument.FromFile("sample.pdf")

' Compress and return as byte array
Dim compressedBytes As Byte() = pdf.CompressPdfToBytes()

File.WriteAllBytes("compressed.pdf", compressedBytes)

If you need a Stream rather than a byte array, call CompressPdfToStream and copy it to your destination. This suits piping output to an HTTP response body, a cloud storage upload, or any stream-based workflow.

:path=/static-assets/pdf/content-code-examples/how-to/pdf-compression-to-stream.cs

using IronPdf;

PdfDocument pdf = PdfDocument.FromFile("sample.pdf");

// Compress and return as Stream
using var compressedStream = pdf.CompressPdfToStream();

using var fileStream = File.Create("compressed.pdf");
compressedStream.CopyTo(fileStream);

Imports IronPdf

Dim pdf As PdfDocument = PdfDocument.FromFile("sample.pdf")

' Compress and return as Stream
Using compressedStream = pdf.CompressPdfToStream()
    Using fileStream = File.Create("compressed.pdf")
        compressedStream.CopyTo(fileStream)
    End Using
End Using

:path=/static-assets/pdf/content-code-examples/how-to/pdf-compression-mode.cs

using IronPdf;

PdfDocument pdf = PdfDocument.FromFile("sample.pdf");

// HighQuality resamples images using the system temp directory, so it produces
// the smallest output but needs write access to that directory at runtime
byte[] compressedBytes = pdf.CompressPdfToBytes(50, false, CompressionMode.HighQuality);

File.WriteAllBytes("compressed.pdf", compressedBytes);

Imports IronPdf

Dim pdf As PdfDocument = PdfDocument.FromFile("sample.pdf")

' HighQuality resamples images using the system temp directory, so it produces
' the smallest output but needs write access to that directory at runtime
Dim compressedBytes As Byte() = pdf.CompressPdfToBytes(50, False, CompressionMode.HighQuality)

File.WriteAllBytes("compressed.pdf", compressedBytes)

Conclusion

You now have one method, CompressAndSaveAs, that re-encodes images and strips the structure tree, plus CompressPdfToBytes and CompressPdfToStream for the same job in memory under a chosen CompressionMode. A natural next step is turning those slimmed-down pages into thumbnails with PDF rasterization.