Compress a PDF so it fits an email attachment limit
"Attachment too large" is one of the most common reasons people look for a PDF compressor. The fix is usually a single pass at Medium — but it helps to know the actual limit you are up against, because they are lower than most people assume once encoding overhead is counted.
Attachment limits by provider
Providers state a total message limit, which covers every attachment plus the message itself. Encoding adds roughly a third to the raw file size, so aim comfortably below the number.
| Provider | Stated limit | Safe PDF size |
|---|---|---|
| Gmail | 25 MB | Under 18 MB |
| Outlook.com | 20 MB | Under 14 MB |
| Microsoft 365 (default) | 25 MB | Under 18 MB |
| iCloud Mail | 20 MB | Under 14 MB |
| Many corporate servers | 10 MB | Under 7 MB |
The fastest route to a sendable file
For a typical scanned contract or report, Medium compression brings the file well inside every limit above while keeping the pages easy to read on screen. Only reach for Maximum when the recipient's server is strict or the document is a long colour scan.
When compression is not the right answer
If the document must stay print-quality — artwork, signed originals for archiving, high-resolution plans — do not compress it to squeeze it into an email. Share a link from cloud storage instead, and send the compressed copy only when the recipient just needs to read it.
Step by step
- 1Open the Compress tool and add the PDF you want to email.
- 2Choose Medium — the balanced default for attachments.
- 3Compare the new size against your provider's safe size above.
- 4Download the compressed copy and attach that file.
Frequently asked questions
- What is the maximum PDF size for Gmail?
- Gmail allows 25 MB per message including all attachments. Because attachments are encoded for transport, keep the PDF itself under about 18 MB.
- Will the recipient notice the compression?
- At Medium, on-screen readability is usually indistinguishable. Differences show up mainly when printing photographs at full size.
- Can I email several PDFs as one file?
- Yes — merge them into a single PDF first, then compress the combined document.
- Is my document uploaded when I compress it?
- Small and Medium compression run in your browser, so nothing is uploaded. Maximum compression is processed on a server and the file is deleted within one hour.
Free, in your browser, no account
Open the tool and get it done in a few seconds.