A PDF export from a phone scan or a design tool can easily balloon to tens of megabytes — too big to email, too slow to upload to a form that caps attachments at 5MB. Compressing it fixes that, but "compress" always trades some quality for size. Here's how to keep that trade sensible.
Steps
- Open Compress PDF and add your file.
- Pick a quality level — higher keeps pages sharper but shrinks the file less; lower shrinks more but softens images and small text.
- Run it and compare the new size against the original, shown once it's done.
What compression actually does here
Each page gets rendered to an image and re-encoded as a JPEG at the quality level you chose, then rebuilt into a new PDF. This is why file size drops so much for scan-heavy documents — image compression is genuinely effective on photos and scanned pages. The trade-off: any selectable, searchable text on the original page is gone afterward, since the page is now an image. If you need to keep text searchable, don't compress that copy — keep the original for reference and only share the compressed one.
Picking a quality setting
- Scanned documents, photos, forms you're archiving: a lower setting is usually fine — the eye tolerates more compression on photographic content than on fine text.
- Documents with small text or fine line diagrams: stay closer to the higher end, or the text can start looking soft/blurry once zoomed in.
- Not sure? Try the default first, check the result, and re-run at a different setting if it's not quite right — it only takes a few seconds since everything runs locally.