Does Compression Always Reduce Quality?
No — and this is a common misconception. PDF compression can be done in two fundamentally different ways:
- 1.Structure optimization — removes redundant data, optimizes internal PDF streams, strips metadata. No visual quality change.
- 2.Image downsampling — reduces the DPI of embedded photos and applies JPEG compression. Does reduce image quality.
PDF.it's Light compression uses approach #1. Medium uses both. Extreme aggressively uses approach #2.
Choosing the Right Compression Level
Light — Best for Quality-Sensitive Uses
Optimizes PDF structure without touching image quality. Size reduction: 15–35%.
Best for: portfolios, presentations, print-ready documents, reports where image quality matters.
Medium — Best Balance
Optimizes structure and reduces image resolution slightly. Size reduction: 40–60%. Minor quality change visible at high zoom.
Best for: email attachments, web sharing, most general use.
Extreme — Maximum Reduction
Aggressively reduces image resolution. Size reduction: 60–90%. Quality visibly reduced on images.
Best for: upload portals with strict size limits (1MB, 2MB, 5MB), archival, mobile sharing.
Text Is Never Affected by Compression
An important clarification: PDF text is stored as vector data — mathematical descriptions of character shapes, not pixels. Vector data scales infinitely without quality loss.
No matter which compression level you choose, text in your PDF will remain crisp, sharp, and readable. Compression only affects raster images (photographs, scanned pages). This means a text-heavy document with minimal images will look identical at any compression level.