Most mail servers cap attachments at 25 MB — Gmail and Outlook both draw the line there, and many corporate gateways cut it at 10 MB. When a PDF blows past that limit, the message bounces or the recipient has to click through a third-party download.
The Compress PDF tool re-serializes the document in your browser and strips unused metadata so the file drops under the threshold without changing the visible content. Nothing uploads to a server, so a contract or invoice you're mailing stays on your machine.
How to use Compress PDF for email attachments
- Open Compress PDF and drop the file you want to attach.
- Wait for the browser to re-encode the PDF — a status line shows the new size in MB.
- If the compressed file is still above your mail provider's limit, run it again with a lower quality setting or split the PDF into two attachments.
- Download the compressed copy and attach it to your email as usual.
Tips that actually matter for this case
- Gmail and Outlook accept up to 25 MB per message, but most inboxes reject anything over 20 MB once base64 encoding overhead is added — aim for 18 MB or lower.
- Scans compress far more than text-only PDFs. If your file is a scanned contract, expect a 60–80% size drop; a text-only report might only shrink 20–30%.
- For very large scanned bundles, run PDF OCR first — the extracted text layer often replaces bulky embedded images and cuts size further.