PDF compression
Also known as: compress PDF, reduce PDF size, shrink PDF file
PDF compression reduces a PDF’s file size, mostly by re-compressing and downsampling the images inside it. It is the standard fix for a PDF that is too large to email or upload, and it keeps the document’s text, layout, and pages intact.
- Most of the savings come from re-compressing embedded images
- Text and layout stay intact; image detail may soften
- Scanned PDFs shrink far more than text-only ones
Why PDFs get large
Most oversized PDFs are heavy because of their images — high-resolution scans, photos, and screenshots embedded at full size. Compression re-encodes those images at a lower resolution or quality and strips unused data, which can cut the file dramatically while the text stays sharp.
Text-only PDFs are already small, so there is little to gain. Scanned documents — which are really page images — usually shrink the most.
Quality trade-off
Stronger compression means smaller files but softer images, so choose a level that keeps scans and photos readable. Compressing an already-compressed PDF again gives diminishing returns and can blur images further, so work from the highest-quality source you have.