How to Compress PDF — Complete Guide
By Docmint Team · · 5 min read
Learn the best methods to reduce PDF file size while maintaining quality. Step-by-step guidance for different document types.
Large PDFs are slow to send, slow to open and often rejected by email servers. The good news is that most PDFs carry far more data than they need to. This guide explains where the bulk comes from and how to remove it without ruining the document.
Why PDFs get big
Three things dominate PDF size: embedded images, embedded fonts and leftover objects from editing. Scanned documents are almost entirely images, which is why a ten-page scan can weigh 30MB while a hundred-page Word export is under 1MB.
Lossless vs lossy compression
Lossless compression rewrites the file structure, removes unused objects and packs data more efficiently. The page content is untouched, so quality is identical. It typically saves 5–30%.
Lossy compression re-encodes images at a lower resolution or quality. On scans and photo-heavy documents it can cut size by 80–90%, at the cost of some sharpness. Text that was real text stays real text only if the tool keeps the vector layer, so check what your tool does.
Step by step
- Open the Compress PDF tool and drop your file.
- Choose Lossless for documents you will print, or Balanced for anything that will be read on screen.
- Compare the before/after size and download.
- If the result is still too large, try Strong, then review a page to make sure the text is readable.
Tips for different documents
Scans: use Balanced or Strong; 110–150 DPI is plenty for reading. Presentations exported from slides: Balanced keeps photos looking good. Contracts and forms: Lossless, so signatures and small print stay crisp.