Compress images inside a PDF — reduce file size

Target only images in a PDF for compression

1 min read·25 July 2026

80–90% of a PDF's file size comes from embedded images. PDFrust's compressImg tool compresses only the images inside a PDF, while keeping text and vector graphics perfectly sharp.

Why compress images separately?

The standard compress tool reduces the whole PDF. The compressImg tool targets only embedded images: lowering JPEG quality, converting PNGs to JPEG where appropriate, and downsampling high-resolution images to screen resolution. Text is not affected.

compressImg vs. compress

Use compressImg when you want maximum control over image quality and absolutely need text quality untouched. Use the regular compress tool for a quick overall reduction. For print files, use neither — keep original resolution.

Compress image

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DPI downsampling

High-resolution images (300+ DPI) embedded in a PDF intended for screen viewing are unnecessarily large. The compressImg tool can downsample images to 96 DPI (screen resolution) or 150 DPI (general use). This dramatically shrinks image data without visible quality loss on screen.

Compare before and after

Download the compressed file and view the images at 100% zoom on your screen. Do they still look sharp? Compression succeeded. Also test by printing if the document is destined for print use.