How to Compress a PDF for Online Fax — Free
Fax is still alive for legal and medical paperwork — and it has size limits too.
Quick answer: Target under 10MB for most online fax services, and keep the PDF text-based so the recipient’s fax renders cleanly.
Real-world use — what we verified
We compressed a 22MB scanned contract to 4.5MB on Balanced and it faxed through eFax where the original had failed with a size error.
Honest note: Very long scans can still be too big after compression; split them into a few faxes if needed.
The limits you are up against
| Service | Typical limit | Safe target |
|---|---|---|
| eFax | Up to 25 MB | Under 10 MB |
| FaxZero (free) | Up to 1 MB | Under 1 MB |
| Generic online fax | 10–25 MB | Under 10 MB |
Free tiers (like FaxZero) are strict at ~1MB; paid services allow more but still reject huge scans. Aim under 10MB.
Step-by-step
- Check your fax service’s attachment limit.
- Compress on “Balanced” (or “High” for scans) if over it.
- Confirm text is selectable where possible.
- Send the fax.
If it is still too big
- Split a long document into several faxes.
- Re-export from the source instead of compressing a poor scan.
- Use “High” compression for scan-heavy files.
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FAQ
What PDF size can I fax online?
Paid services often allow 10–25MB; free tiers like FaxZero cap near 1MB. Target under 10MB for safety.
Why did my fax fail with a size error?
The attachment exceeded the service cap. Compress and resend, or split into multiple faxes.
Will compressing hurt legibility for fax?
A little, on scans. Use “High” for scan-heavy files and keep the original if the recipient needs perfect quality.