How to compress a PDF without losing quality
Most PDF compressors trade size for ugly text and blocky images. Here's how to get the savings without the regret.
By PDFOnly Team · April 12, 2026 · 6 min read
If you've ever shrunk a PDF and ended up with a blurry mess, you're not alone. Most online compressors flatten everything to the same low DPI, which crushes detailed images and pixelates text. The trick to compressing well is to be selective: keep text at full fidelity and only downsample images.
We do this by default. Behind the scenes, PDFOnly uses Ghostscript with a content-aware preset that:
1. Subsets fonts so they only embed the glyphs the document actually uses. 2. Recompresses embedded images using more efficient codecs (JPEG2000 / JPEG with quality tuning). 3. Downsamples images intelligently — color photos to 150 DPI for "Recommended", 72 DPI for "High".
For image-heavy documents the savings are typically dramatic (often more than half). Text-only PDFs see less because they're already small to begin with.
When "High" compression is the right call
Use the High preset when you absolutely must get under a hard size cap (1 MB email limits, 100 KB government portals). Expect visible degradation in color photos but text remains readable.
When "Low" compression is right
Choose Low if you'll print the document. Print needs 300 DPI to look professional, and aggressive compression will show through.
A neat trick: OCR first, then compress
Scanned documents are images, not text. Compressing an image-only PDF produces blurry savings. If you OCR first, the recognized text stays sharp at any compression level — only the underlying scans get smaller. The Recommended preset on a freshly OCR'd PDF is usually the sweet spot.