Glossary / PDF Compression
What Is PDF Compression?
PDF compression reduces a PDF file's size by optimizing embedded images, removing redundant data, and applying compression algorithms. The goal is to make files smaller for easier sharing and storage while maintaining acceptable visual quality.
How PDF compression works
PDFs typically contain three types of data that can be compressed: images (often the largest component), fonts, and page content streams. Compression algorithms like Flate (zlib/deflate) handle text and vector data losslessly, while image data can be recompressed using JPEG for photographs or PNG-style compression for graphics.
Additional optimization techniques include removing duplicate font subsets, stripping unused metadata, flattening form fields, and downsampling high-resolution images to a target DPI. A well-optimized PDF can be 50-90% smaller than the original.
Lossless vs lossy
Lossless compression preserves every pixel and glyph exactly. Lossy compression sacrifices some image quality for dramatically smaller file sizes. Most PDF compression tools offer quality presets that balance size reduction against visual fidelity.
Related tools on fixtdoc
- Compress PDF , reduce PDF file size while keeping readability
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