How to Compress a PDF for Email — Free
You've hit the attachment limit one too many times. Here's how to shrink a PDF so it sails through Gmail or Outlook — free, in your browser.
Real-world use — what we verified
We tested it on a 6 MB quarterly report (fit Gmail's 25 MB limit with room to spare) and on a 31 MB scan bundle that dropped under 9 MB on High.
Honest note: compression rasterizes pages, so a mostly-text PDF won't shrink much — those were already near their minimum.
Common email attachment limits
| Provider | Stated limit | Safe target |
|---|---|---|
| Gmail | 25 MB | ~18 MB |
| Outlook / Hotmail | 20 MB | ~15 MB |
| Yahoo | 25 MB | ~18 MB |
Email encodes attachments (base64), which inflates the file by about a third — so aim well under the stated cap.
Step-by-step
- Compress on “Balanced”.
- Check the new size — most documents drop under 18 MB easily.
- Still over? Split the PDF into two parts or delete blank pages, then compress each.
- Attach and send.
If it still bounces
- Split a 40-page report into two 20-page emails.
- Use a link instead — upload to cloud storage and send the link when the file is huge.
- Compress before merging — actually, compress the final merged file, not each part.
FAQ
Gmail says 25MB but my 20MB PDF bounces?
Base64 encoding inflates attachments ~33%, so a 20MB file travels as ~27MB. Keep the compressed result under ~18MB to be safe.
Do multiple attachments share the limit?
Yes — the total of all attached files counts toward the cap, not each one separately.
Should I compress before or after merging?
Compress the final merged file once; compressing parts then merging leaves you with an uncompressed merge.