How PDF compression actually works
Most of a PDF's size comes from embedded images (scans, photos, charts), not text. Our compressor renders each page to a canvas at a chosen resolution, re-encodes it as a JPEG at your chosen quality, and rebuilds a new PDF from those images.
Text becomes slightly less crisp (it's now an image), but file size drops dramatically — typically 60–90% for scanned documents.
Step-by-step
- 1Open the Compress PDF tool.
- 2Upload your PDF — the original size is shown.
- 3Pick image quality: 60% is a great default. Lower for smaller, higher for sharper.
- 4Pick resolution: 1.2× works for screen viewing; bump to 2× if you need to print.
- 5Click Compress PDF. You'll see the new size and the % reduction.
Recommended settings by use case
- Email a contract — quality 65%, resolution 1.5× (good balance).
- WhatsApp / Telegram — quality 55%, resolution 1.0× (smallest).
- Government portal under 2 MB — start at quality 50%, resolution 1.0×, raise quality until you hit the limit.
- Printing at home — quality 80%, resolution 2.0× (keep it crisp).
When compression won't help much
Text-only PDFs (born-digital invoices, exported reports) are already tiny — compression may even increase size because everything gets rasterized.
If your file is mostly vector graphics or selectable text, prefer to keep it as-is or use a more advanced tool.
What makes a PDF large in the first place
Most large PDFs are large because of embedded images, not text. A 50-page contract is a few hundred kilobytes; a 50-page scanned brochure is 30 MB because every page is a high-resolution JPEG. Compression works by re-encoding those embedded images at a lower (but still readable) DPI, swapping the encoding to a more efficient codec (JPEG2000, JPEG XR) where supported, removing duplicate fonts, and dropping cached thumbnails and per-page metadata. Text-only PDFs are already efficient — expect 10-20% savings — but image-heavy PDFs routinely shrink 60-80%.
Choosing a compression level
- Email-friendly (~150 DPI): keeps print readability, fits 100-page documents under the 25 MB Gmail limit.
- Screen-quality (~96 DPI): perfect for reading on a laptop or sharing on a Slack/Teams channel; cuts size roughly in half again.
- Web-quality (~72 DPI): smallest output; ideal for embedded previews on a website where users can request the full version.
- If unsure, start with email-friendly and only step down if the file is still too big for your channel.
When to split instead of compress
If the PDF is a long report and the recipient only needs a section, splitting (extracting just chapter 3) is more useful than compressing all 200 pages. If the file is a batch of invoices, splitting one-per-PDF is friendlier for the recipient's filing system than a single megabyte-saving compress. Combine compress with split when you want both: split first, then compress each part.
FAQ
- Will the text still be selectable after compression?
- No — our compressor flattens pages to images. If you need selectable text, keep your original and only share the compressed copy.
- How much smaller can I get a PDF?
- Scanned PDFs commonly shrink 70–90%. Born-digital PDFs may shrink 0–30% or even grow slightly.
- Is the original modified?
- No. The tool downloads a new compressed file — your source PDF is untouched.