Reduce PDF Size Without Quality Loss — What That Actually Means
2026-06-03 5 min read
The promise 'no quality loss' is a simplification. Here is what actually compresses losslessly vs lossily in a PDF and what realistic size reductions to expect.
"Reduce PDF size without quality loss" is a slight overstatement. Compression always involves trade-offs. The accurate version is "without visible quality loss" -- degradation below the threshold where a typical reader notices. Here is what that means in practice.
What compresses losslessly vs lossily
- Text and vector graphics: Compress losslessly with Deflate/ZIP. Zero quality degradation.
- Raster images (photos, scans): Typically compressed with JPEG. Lower quality means smaller files, with visible artifacts if pushed too far.
- Embedded fonts: Font subsetting (only characters actually used) reduces size losslessly.
What makes PDFs bloated
Most bloated PDFs have one of three problems: duplicate embedded font data, images at print resolution when the file will only be read on screen, or revision history from Word dragged into the export. The PDF Compressor uses Ghostscript WASM to address all three in one pass.
Realistic size reduction numbers
- PDF from Word with images: 40-60% at eBook quality
- Scanned PDF at 300 DPI: 60-80% at Screen quality
- Native text-only PDF: 10-30%
- Already-compressed PDF: 5-10% further