PDF Compression: Lossy vs Lossless Explained

When compressing PDFs, there are two approaches: lossy and lossless.

Lossless Compression

Reduces file size without any quality loss by:

• Removing unnecessary metadata
• Cleaning internal structure
• Using efficient encoding (object streams)
• Removing duplicate resources

Typical reduction: 10-30%

Best for: Legal documents, contracts, print-ready files

Lossy Compression

Greater reduction by optimizing images. Text and vectors are never affected.

• Reduces image resolution
• Applies JPEG compression to images

Typical reduction: 40-80%

Best for: Email, web uploads, general sharing

Which to Use?

For most everyday use, Medium or High compression is ideal. Quality loss is usually imperceptible on screens.

Technical Details

Lossless compression uses algorithms like DEFLATE and LZW. Lossy compression uses JPEG and JPEG2000 for images. Modern compressors combine both techniques for optimal results.