How to Reduce PDF Size for Email (Gmail 25 MB, Outlook 20 MB)
A PDF that's too big for an email or an upload form is a daily annoyance — especially scanned documents, which can run to tens of megabytes. Here are the real limits and the fastest ways to get under them, without sending your document to someone else's server.
Attachment limits in 2026
| Provider | Send limit | Receive limit |
|---|---|---|
| Gmail | 25 MB | 50 MB |
| Outlook.com / Hotmail | 20 MB | 20 MB |
| Microsoft 365 (work) | 35 MB default (admins can raise it to 150 MB) | 36 MB default |
| Yahoo Mail | 25 MB | 25 MB |
| iCloud Mail | 20 MB (Mail Drop up to 5 GB) | 20 MB |
| Proton Mail | 25 MB | 50 MB |
The catch: email encodes attachments in Base64, which makes them about 33–37% larger in transit. So a "25 MB" limit really means about 18 MB of file. If you send to many recipients whose limits you don't know, aim for under 10 MB.
Why PDFs get big
- Scans: every scanned page is a full-page photo, often at 300–600 dpi in colour.
- Embedded photos: PDFs exported from slides or design tools often keep images at full camera resolution.
- Fonts and duplicate objects: smaller, but they add up in long documents.
Text-only PDFs exported from Word or Google Docs are usually small already — a 20-page report is often under 1 MB.
Four ways to shrink a PDF
- Re-render the pages at 150 dpi. This is the biggest win for scans, typically cutting the size by 60–90% while staying readable on screen and in print. The PDF compressor's "Balanced" mode does this, and "Strong" (110 dpi) goes further. The trade-off: text in the result can't be selected or searched.
- Lossless clean-up first. For text PDFs, the lossless mode rewrites the file structure without touching quality. Gains are smaller, but nothing is lost.
- Grayscale. Black-and-white documents scanned in colour shrink a lot more when converted to grayscale.
- Send fewer pages. Remove pages nobody needs with Delete PDF pages, or split the document into two emails.
If you are building the PDF from phone photos, shrink the images first — JPG to PDF has an "Email" quality preset (1,600 px at 70%) that keeps ten photos to roughly 3–5 MB.
Keep confidential files off the internet
Most online PDF compressors upload your file to their servers. That's a real risk for bank statements, ID documents or contracts. ToolFeather's PDF tools run entirely in your browser — the file never leaves your device — using Mozilla's pdf.js and the open-source pdf-lib library.