How to Reduce a PDF's File Size So You Can Email It
PDF too big to attach? Learn the attachment limits for Gmail, Outlook and Yahoo, and how to shrink a PDF in your browser so it sends the first time.
Quick answer
- Gmail and Yahoo accept attachments up to 25 MB; Outlook allows about 20 MB. Many work email systems are stricter.
- Scanned pages and photos are what make PDFs big — compressing those images is the fastest win.
- If compression isn't enough, remove pages you don't need, convert scans to grayscale, or send it in parts.
You hit Send and get a bounce-back: the attachment is too large. It happens most with scanned contracts, photo-heavy reports and documents exported from design tools. The good news is that most oversized PDFs can be cut down to a fraction of their size in under a minute, without installing anything.
How big can an email attachment be?
The limit depends on the email service, and it applies to the whole email — all attachments added together.
| Email service | Attachment limit | What happens above it |
|---|---|---|
| Gmail | 25 MB | Gmail offers to send a Google Drive link instead |
| Outlook / Outlook.com | About 20 MB | Outlook.com offers a OneDrive link instead |
| Yahoo Mail | 25 MB | The file can't be attached |
| Company email | Often 10 MB, sometimes 5 MB | The message bounces back |
Also keep the person receiving the file in mind: if their company caps incoming mail at 10 MB, your 18 MB PDF bounces even though Gmail let you send it. Aiming for under 10 MB is the safest choice for anything going to a business.
Why is my PDF so big?
Text takes up almost no space in a PDF — a 100-page novel can be under 1 MB. What makes PDFs heavy is images: scanned pages (every scanned page is a photo), pictures taken on a phone, and high-resolution graphics. A single phone photo can be 3–5 MB on its own, so a 10-page scan can easily pass 25 MB.
That's why compression works so well on scanned and image-heavy PDFs, and why it does very little for a PDF that's already mostly text.
How to compress a PDF for email, step by step
- 1
Open Compress PDF
Go to Compress PDF on PDFDoco. It works in any browser, on a computer or a phone.
- 2
Add your PDF
Drag the file onto the page or tap to choose it. It's processed in your browser — the file is never uploaded to a server.
- 3
Pick a compression level
Start with Recommended. It gives the best balance of size and quality for documents you'll read on screen.
- 4
Compress and check the size
Click Compress PDF, then compare the new size with your email limit. If it's still too big, run it again with Extreme Compression.
- 5
Download and attach
Open the file once to check it's readable, then attach it to your email.
Good to know: PDFDoco's compressor rebuilds each page as an optimised image. That's what makes it so effective on scans, but it also means text in the compressed file can't be selected or searched. Keep your original if you'll need to copy text from it later.
Free, private and done in your browser.
Compress your PDFStill too big? Four more ways to shrink it
1. Remove pages you don't need to send
Cover sheets, blank pages and appendices add weight. Use Delete PDF Pages to drop them, or Split PDF to keep only the pages the recipient needs.
2. Convert a scan to grayscale
Colour scans of black-and-white documents waste space. Grayscale PDF converts every page to shades of grey, or to pure black and white, which is ideal for printed forms and letters.
3. Send it in two parts
If a long report won't go under the limit, split it into two files with Split PDF (for example pages 1–40 and 41–80) and send two emails, labelled "Part 1 of 2" and "Part 2 of 2".
4. Share a link instead
For very large files — design proofs, full-resolution scans — upload the file to Google Drive, OneDrive or Dropbox and paste the share link into your email. Gmail and Outlook.com will offer to do this for you automatically.
Tip: Zipping a PDF rarely helps. PDFs are already compressed internally, so a ZIP file of a PDF usually saves only a few percent.
Preventing oversized PDFs next time
- When scanning, choose 150–200 DPI and grayscale for ordinary documents. 300 DPI colour is only needed for photos or print.
- When exporting from Word or PowerPoint, choose the "Minimum size" or "Online publishing" option instead of "Standard" or "High quality print".
- Turning photos into a PDF? Use JPG to PDF, then compress the result before sending.
Frequently asked questions
What is the maximum PDF size for Gmail?
Gmail lets you attach up to 25 MB per email, counting all attachments together. Above that, Gmail offers to send the file as a Google Drive link instead.
Will compressing a PDF reduce its quality?
Some image detail is traded for size. With the Recommended level, documents stay clear to read on screen. If you need maximum sharpness for printing, use Less Compression or keep the original.
Why did my PDF get bigger after compressing?
This can happen with PDFs that are mostly text and already small, because PDFDoco rebuilds pages as images. If your PDF is text-only and under a few megabytes, it's usually small enough to email already.
Is it safe to compress confidential documents online?
With PDFDoco, yes — the compression runs inside your browser, so the file never leaves your device and is never uploaded to our servers.