Compress a PDF to under 500 KB
Reduce a PDF to half a megabyte for email attachments and portal uploads, keeping as much resolution as the target allows. Nothing is uploaded.
- Runs in your browser
- Files are never uploaded
- Free, no account
Half a megabyte, and why it is a good default
500 KB is rarely a hard limit imposed by a form. It is more often the number people choose for themselves once an attachment has bounced, and it is a sensible one: comfortably under every mail gateway, quick to open on a phone over mobile data, and generous enough that a ten-page document still looks like a document rather than a fax.
Where it does appear as a rule, it is usually a content management system, a helpdesk ticketing tool, or a supplier portal that wants to keep its own storage predictable.
Email attachment limits, for reference
| Service | Typical per-message limit |
|---|---|
| Gmail | 25 MB (larger files switch to a Drive link) |
| Outlook.com | 20 MB |
| Microsoft 365 / Exchange | Commonly 25–35 MB, often lowered by an administrator |
| iCloud Mail | 20 MB |
| Older corporate gateways | 5–10 MB, sometimes 2 MB |
The published limit is not the whole story. Attachments are base64-encoded in transit, which adds about 33 per cent, and the strictest hop in the chain wins — your outbound limit does not help if the recipient's gateway is tighter. Aiming at 500 KB removes the whole class of problem.
Photo-heavy documents behave differently
Text scans and photographs compress in opposite directions. A page of black text on white is mostly flat area, which JPEG encodes almost for free; a photograph is continuous tone in every block, which it cannot.
- A twelve-page text scan at 500 KB will usually finish at quality 60–75 and look clean.
- A twelve-page brochure with full-bleed photography will be pushed into the thirties and show banding in skies and gradients.
If the document is a portfolio, a property listing or a product catalogue, start at 1 MB or 2 MB and only come down if something insists.
Choosing the resolution yourself
The automatic setting divides your target by the page count and picks a DPI from that. It is a good default, but there are two cases where overriding it wins:
- Small print matters more than smoothness. A contract with 6-point footnotes reads better at 150 DPI and quality 40 than at 96 DPI and quality 75, even though the second looks "cleaner" at a glance. Force the higher DPI.
- The page is a photograph. The opposite applies: drop to 96 or 72 DPI so the encoder has quality to spend, because banding is more objectionable than softness in a picture.
What is lost, stated once
Reaching a byte target means re-rendering pages as images. Three things go with that, and no setting brings them back:
- the text layer — the output is no longer searchable or selectable;
- vector sharpness — a line drawing becomes pixels and will not stay crisp when zoomed;
- document metadata, bookmarks and links — the file is rebuilt from scratch, so those do not carry over.
If none of that is acceptable, the lossless clean-up mode in Compress PDF rebuilds the file structure without touching page content. It typically saves far less, but it keeps everything.
Questions
Is 500 KB a sensible target for emailing?
It is a good default. Most corporate mail gateways start rejecting attachments somewhere between 10 MB and 25 MB, but anything under a megabyte also avoids clogging a recipient with a slow connection.
Will 500 KB keep a photo-heavy brochure looking good?
Partly. Photographs compress worse than text scans, so a ten-page brochure at 500 KB will show JPEG artefacts in gradients. Try 1 MB or 2 MB first and only come down if the form insists.
Can I choose the rendering resolution myself?
Yes. Open the resolution options and pick 72, 110, 150 or 200 DPI instead of letting it choose. A higher DPI keeps small print sharp but forces the quality search lower to stay inside the same byte budget.
Does compressing remove metadata?
Yes, as a side effect. The output is rebuilt from scratch as image pages, so the original author, producer, creation date and any XMP block do not carry over.