How to Compress a PDF Without Losing Quality (2026)

Big PDFs slow down email, websites, and downloads — but aggressive compression can make text fuzzy and photos grainy. Here's how to cut file size 70–90% without anyone noticing the difference.

Key takeaways

  • Image downsampling is responsible for 90% of compression savings
  • 'Screen' preset for email/web, 'Print' preset for print shops
  • Always preview the compressed file before sending
  • Born-digital PDFs barely shrink — that's normal

Where the size actually comes from

9 times out of 10, an oversized PDF is oversized because of images — scanned pages at 600 DPI, photos in a brochure, screenshots embedded at full resolution. Compression mainly attacks images: downsample to a screen-friendly DPI, re-encode in JPEG or JBIG2, and the file shrinks dramatically.

Pick the right preset

Three presets cover most use cases. 'Screen' (around 100–150 DPI) is ideal for email and web — text stays sharp at normal zoom, file size drops 70–90%. 'eBook' (around 150 DPI) keeps slightly better detail for tablet reading. 'Print' (300 DPI) is for documents going to a printer — minimal size reduction, no quality loss.

Step-by-step

Upload your PDF, choose 'screen' or 'eBook' preset, click Compress, and download the result. Always open the compressed file before sending — zoom in on a detailed page and confirm text is still crisp. If anything looks off, re-do with the next-better preset.

What not to do

Don't compress an already-compressed PDF — you'll just degrade quality without much size benefit. Don't compress PDFs that are already small (under 1 MB) — there's nothing to save. Don't use 'screen' preset on documents you'll print — text will look soft.

Born-digital PDFs barely shrink

If your PDF was exported from Word or another office app, it's probably already small. Don't be surprised if a 200 KB invoice only drops to 180 KB — there's almost no image data to compress.

Frequently asked questions

Will compression make my PDF look worse?

Only if you pick too aggressive a preset. 'Screen' or 'eBook' are virtually invisible on screens. 'Aggressive' or under-100-DPI presets will visibly degrade text and photos.

Why didn't my PDF shrink?

Probably already optimised. Born-digital PDFs (Word/Excel exports) have very little to compress. Scan-heavy PDFs are where compression shines.

Is compression lossy?

Image compression is usually lossy (JPEG); text and vector compression (Flate) is lossless. Most compressors blend both to maximise savings without visible quality loss.

Is online PDF compression safe?

Reputable services delete files within minutes. Avoid uploading confidential documents to free services without checking their retention policy.