If your email bounces or your mail app offers to send a cloud link instead, your PDF is over the attachment limit. The fix is usually quick: compress the PDF, and most files shrink dramatically.
Email attachment limits
| Email service | Attachment limit | What happens above it |
|---|---|---|
| Gmail | 25 MB | Gmail offers to send a Google Drive link instead |
| Outlook.com | 20 MB | Outlook offers to share the file from OneDrive |
| Yahoo Mail | 25 MB | Large files must be shared another way |
| iCloud Mail | 20 MB | Mail Drop can send files up to 5 GB as a link that expires after 30 days |
| Work email | Set by your company | Often lower than the services above |
These limits are for all attachments in one message combined. Some mail servers measure the encoded size of an attachment, which is about a third larger than the file on your computer, so a 20 MB PDF can bounce at a server with a 25 MB limit. Aim to stay comfortably below the limit.
Why is your PDF so big?
Text takes up very little space. A 50-page contract typed in Word is often well under 1 MB. Large PDFs are nearly always large because of images:
- Scanned pages are photos of paper. A color scan at 600 dpi can be several megabytes per page.
- Phone photos placed into a document keep their full resolution, even when they appear small on the page.
- Design files and presentations exported to PDF often contain high-resolution graphics.
That's good news: images can be shrunk a lot without making the document hard to read.
How to compress a PDF for free
- Open Compress PDF and choose your file.
- Pick a level. Recommended works for most documents and keeps text selectable. Use Strong for scanned documents; it often reduces them by 80–95%.
- Check the new size, then download the smaller copy.
The compression runs in your browser, so your document is never uploaded, which matters for tax returns, contracts and medical records. If your file needs to be under a specific size, such as 1 MB for an upload form, the PDF Size Reducer keeps trying until it gets there.
Still too big? Other options
- Split it. Use Split PDF to send the document in two or three emails.
- Send a link. Upload the file to Google Drive, OneDrive, Dropbox or iCloud and share a link. There's no size limit for the recipient to deal with.
- Scan again at a lower resolution. 150–200 dpi is plenty for reading on screen, and grayscale is much smaller than color for text documents.
- Export smarter from Word. On Windows, choose Save As → PDF and pick "Minimum size (publishing online)" instead of "Standard".
- On a Mac, Preview can reduce file size (File → Export, then the Quartz Filter "Reduce File Size"), but it often makes images look noticeably blurry. Check the result before sending.
What won't shrink much
PDFs that are almost all text, like typed contracts or reports, are already small, and compression can't do much for them. If such a file is still large, it may contain embedded fonts or a hidden high-resolution image such as a logo or signature. Compressing still helps a little; splitting or sending a link is usually the better fix.
Keep the original
Always keep your original file. Strong compression turns scanned pages into lower-resolution images, which is fine for reading but not ideal for printing or archiving. Once the email has been sent, delete the compressed copy if you don't need it.
Need to send several documents as one? Combine them into a single PDF first, then compress the result.
Frequently asked questions
Will compressing a PDF reduce its quality?
How do I email a PDF larger than 25 MB?
Is it safe to compress a PDF online?
Tools mentioned in this guide
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