How to Compress PDF Files in Java

How Do I Compress a PDF File in Java?

IronPDF compresses PDF files by targeting the embedded images inside the document. The compressImages() method accepts a quality integer from 0 to 100, where lower values produce smaller files at the cost of image sharpness. An optional second parameter instructs the library to scale down image resolution based on the display size in the PDF page.

//:path=/static-assets/pdf/content-code-examples/java/how-to/compress-pdf-java-tutorial/compress-pdf-images.java
import com.ironsoftware.ironpdf.*;
import java.io.IOException;
import java.nio.file.Paths;

public class App {
    public static void main(String[] args) throws IOException {
        // Load the source PDF from disk
        String src = "C:\\Image based PDF.pdf";
        PdfDocument pdf = PdfDocument.fromFile(Paths.get(src));

        // First pass: compress images to 60% quality
        // Lower values produce smaller files with more visible quality loss
        pdf.compressImages(60);
        pdf.saveAs(Paths.get("assets/document_compressed.pdf"));

        // Second pass (optional): compress to 90% quality with resolution scaling
        // The second parameter scales image resolution down to match display size,
        // which can reduce file size further but may cause distortion in some PDFs
        pdf.compressImages(90, true);
        pdf.saveAs(Paths.get("C:\\Compressed.pdf"));
    }
}

//:path=/static-assets/pdf/content-code-examples/java/how-to/compress-pdf-java-tutorial/compress-pdf-images.java
import com.ironsoftware.ironpdf.*;
import java.io.IOException;
import java.nio.file.Paths;

public class App {
    public static void main(String[] args) throws IOException {
        // Load the source PDF from disk
        String src = "C:\\Image based PDF.pdf";
        PdfDocument pdf = PdfDocument.fromFile(Paths.get(src));

        // First pass: compress images to 60% quality
        // Lower values produce smaller files with more visible quality loss
        pdf.compressImages(60);
        pdf.saveAs(Paths.get("assets/document_compressed.pdf"));

        // Second pass (optional): compress to 90% quality with resolution scaling
        // The second parameter scales image resolution down to match display size,
        // which can reduce file size further but may cause distortion in some PDFs
        pdf.compressImages(90, true);
        pdf.saveAs(Paths.get("C:\\Compressed.pdf"));
    }
}

The code loads a PDF from disk and applies compression in two passes to illustrate different strategies. The first compressImages(60) call reduces image quality to 60% and saves the result. The second call uses 90% quality but enables resolution scaling, which adjusts each image's pixel dimensions to match its visible area on the page.

The compressImages() method has two signatures:

• compressImages(int quality) — Resamples all embedded images to the given JPEG quality level. Use a value between 40 and 80 for strong size reduction while keeping images recognizable.
• compressImages(int quality, boolean scaleImageResolutionToVisibleSize) — Adds resolution scaling. When true, the library detects images that are rendered at a fraction of their native resolution and scales them down accordingly. This option offers the most aggressive size reduction but increases processing time slightly.

Running a 60% compression pass on an image-heavy PDF typically reduces file size by 50-70% depending on the source images. A document with primarily text content will see much smaller gains. Compare the before and after file sizes in the output directory to evaluate the result for your specific documents.

For documents that need other processing alongside compression, IronPDF supports extracting text, extracting images, and splitting PDFs.

How Do I Choose the Right Compression Quality Setting?

Choosing the correct quality level requires balancing file size against visual fidelity. The right setting depends on the document's purpose and the sensitivity of its embedded images.

The table below gives practical guidelines for common use cases:

Resolution scaling works best when the source PDF was assembled from high-resolution photographs or scanned pages but the document is intended only for screen viewing. In those cases, scaling resolution can reduce file size without a perceptible change in quality at normal zoom levels. For further context on PDF image encoding standards, refer to the JPEG 2000 format documentation at the Library of Congress and the PDF image compression discussion on Stack Overflow.

How Do I Reduce PDF File Size Further Beyond Image Compression?

Image compression handles the largest contributor to file size in most PDFs, but additional techniques can reduce size further when combined. IronPDF supports several approaches that complement compressImages():

Remove unneeded pages. Deleting pages before compressing reduces both image data and page structure overhead. Use the page deletion examples to remove blank or redundant pages first.

Strip annotations. Annotation objects add binary data to the file. Removing them with the annotation management API before saving can reduce file size noticeably in documents with heavy markup.

Process documents in bulk. For workflows that compress many PDFs, iterate over a list of file paths and apply compressImages() in a loop. IronPDF handles each document independently, so batch processing does not require special configuration — see the pdf-compression example for a starting point.

For a broader discussion of PDF optimization strategies, the PDF file format specification at the Library of Congress documents the structural elements that contribute to file size and how they can be reduced.

What Are the Next Steps for Compressing PDFs in Java?

IronPDF's compressImages() method provides a practical way to reduce PDF file size in Java applications. A single method call with a quality integer covers most use cases, and the optional resolution scaling parameter handles image-heavy source files that need the most aggressive reduction.

Start with a free trial to test compression on your own documents:

• Start your free trial — no credit card required
• View licensing options — licenses start from $999

Ready to see what else IronPDF can do? Check out the full Java PDF tutorial library here: IronPDF Java How-To Guides