To compress a PDF for email, shrink the images inside it. Run the file through a PDF compressor at a balanced setting, which resamples photos and scans to roughly 150 dpi and re-encodes them as JPEG, then check the new size against your limit. Gmail, Yahoo Mail and Outlook.com accept 25 MB per message and iCloud Mail 20 MB, but aim for 10 MB or less so the email also gets through stricter company mail servers. If compression alone isn’t enough, delete pages you don’t need, split the file or send a cloud link.
Email attachment limits in 2026
These are the published limits for the big personal email services. Providers change them occasionally, so if a send fails, check your provider’s help pages.
| Email service | Limit per message | If you go over |
|---|---|---|
| Gmail | 25 MB of attachments | Gmail swaps the file for a Google Drive link |
| Yahoo Mail | 25 MB of attachments in total | Share a cloud storage link instead |
| Outlook.com | 25 MB, including the message text | Share the file as a OneDrive link |
| Outlook desktop app (non-Exchange accounts) | 20 MB by default | “Attachment size exceeds the allowable limit” error |
| iCloud Mail | 20 MB | Mail Drop sends a download link for files up to 5 GB |
| Work email (Microsoft 365, Exchange) | Set by your IT team | The message bounces back to you |
Two things catch people out:
- The limit is per message, not per file. Three 9 MB PDFs on one email add up to 27 MB, which is too big for Gmail.
- The recipient’s limit matters too. Attachments are base64-encoded when they’re sent, which makes them about a third bigger on the wire. Some corporate mail servers still use the old Exchange default of 10 MB. A 15 MB PDF can leave your Gmail fine and still be rejected by your accountant’s or HR department’s server.
Upload portals for job applications, universities, courts and government agencies (the IRS, HMRC, the CRA, the ATO) set their own per-file limits. These are often only a few megabytes. The limit is usually printed next to the upload button, so check it before you start compressing.
Why your PDF is so big
PDFs that contain only text are tiny. A 20-page report exported from Word is often under 1 MB. The size comes from images, and especially full-page images:
- Scanned documents. Every page is a photo of paper.
- Phone photos turned into PDFs. A 12-megapixel photo is 4032 × 3024 pixels.
- Brochures and slide decks with high-resolution photos.
Here’s the arithmetic for one US Letter page (8.5 × 11 in) scanned in colour at 300 dpi:
- Pixels: (8.5 × 300) × (11 × 300) = 2,550 × 3,300 = 8,415,000 pixels
- Uncompressed colour data: 8,415,000 × 3 bytes = about 25 MB per page
JPEG compression inside the PDF brings that down a lot, but a page that is mostly photo or grey paper texture often still weighs 1 MB or more. Scan the same page at 150 dpi and you get 1,275 × 1,650 = 2,103,750 pixels. That’s one quarter of the data, and on screen it’s still perfectly readable. A4 pages (8.27 × 11.69 in) work out almost the same: 2,480 × 3,508 pixels at 300 dpi.
So the biggest saving comes from downsampling: lowering the image resolution to what the reader actually needs. Lowering JPEG quality helps too.
How to compress a PDF step by step
- Open Compress PDF and drop your file in. It’s processed in your browser, so a payslip or medical letter is never uploaded to a server.
- Leave the level on Recommended and click Compress PDF.
- Compare the before and after sizes shown next to the download button. If you’re under your limit, download and you’re done.
- If it’s still too big, try Strong. For a scanned document that still won’t fit, try Extreme.
- Open the result and zoom to 100% to check that small print, signatures and stamps are still legible before you send it.
If the PDF can’t be made smaller, the tool tells you and gives you back the original file. It won’t hand you a bigger one.
Which compression level to choose
| Level | What it does to images | Text stays selectable? | Best for |
|---|---|---|---|
| Light | Nothing; rewrites the file structure losslessly | Yes | Text-only files with a little bloat |
| Recommended | Larger images capped at 1,700 px on the longest side (about 150 dpi for a full page), moderate JPEG quality | Yes | Most PDFs: reports, forms, mixed text and photos |
| Strong | Capped at 1,100 px (about 100 dpi), lower JPEG quality | Yes | Photo-heavy files that must fit a tight limit |
| Extreme | Rebuilds every page as one JPEG image at about 100 dpi | No, pages become pictures | Scans that still won’t fit |
Recommended and Strong only touch embedded images, so typed text and vector graphics stay sharp at any zoom. Extreme flattens everything into pictures. Use it for scans, which are pictures already, and avoid it for documents someone needs to search or copy text from.
Worked example: a 24-page colour scan
Say a scanned lease comes out at 30 MB: 24 pages at about 1.25 MB each, scanned at 300 dpi.
- Downsampling to roughly 150 dpi keeps a quarter of the pixels, so the image data drops to around 25% of the original before any quality change.
- That puts the file somewhere near 7–8 MB before lower JPEG quality squeezes it further.
The exact result depends on the scan, but a drop like this is typical for colour scans. A 30 MB PDF of typed text with a few logos won’t change much, because there’s very little image data to shrink.
When compression isn’t enough
Remove pages you don’t need. Blank backs of double-sided scans, cover sheets and terms-and-conditions pages add size for nothing. Mark them in Delete PDF Pages or type a range like 2, 5-7.
Split the file and send it in parts. Split PDF can cut a document into fixed ranges (for example 1-12, 13-24) or into chunks of N pages, then download them as a ZIP. Name the parts clearly (“Lease part 1 of 2”) so the recipient knows to expect both.
Re-export from the original file. If you made the PDF yourself, exporting again with smaller settings often beats compressing afterwards:
- Word on Windows: File › Save As › PDF, then set Optimize for to Minimum size (publishing online).
- Word on Mac: File › Save As › PDF and choose Best for electronic distribution and accessibility.
- Mac Preview: File › Export, then set the Quartz Filter to Reduce File Size. It’s aggressive, so check photos afterwards.
Rescan at a lower setting. For typed documents, 200–300 dpi in greyscale or black and white produces far smaller files than colour, and text stays crisp. Colour is only needed for photos, highlighter marks or coloured stamps.
Build photo PDFs with a lower quality setting. If you’re turning phone photos of receipts or forms into a PDF with JPG to PDF, drop the Image quality slider to around 60–75% and choose a fixed page size such as Letter or A4. The tool keeps every photo’s full pixel dimensions, so for very large images you can shrink them first with Resize Image, or simply run the finished PDF through Compress PDF on Recommended.
Send a link instead. Gmail (Google Drive), Outlook (OneDrive) and iCloud Mail (Mail Drop) can all send a download link instead of an attachment. That’s the right choice for anything over 25 MB that has to stay full quality, such as architectural drawings or print-ready artwork.
Password-protected and restricted PDFs
Encrypted PDFs have to be opened before they can be compressed. If the file has restrictions on printing or editing, or has a password you know, remove them first with Unlock PDF, then compress. If the document is sensitive, add protection back afterwards with Protect PDF. Always compress first, then encrypt, and send the password by a different route, such as a text message or a phone call, not in the same email.
FAQ
What size should a PDF be for email?
Under 10 MB is the safe target. It fits every major provider’s limit with room for base64 encoding, and it gets through stricter corporate servers. Gmail, Yahoo Mail and Outlook.com accept up to 25 MB per message, and iCloud Mail 20 MB.
Does compressing a PDF reduce quality?
Only the images change. At the Recommended level, typed text and vector graphics are untouched, and photos are kept at around 150 dpi, which looks sharp on screen and prints acceptably. Strong and Extreme trade more image detail for size.
Why won’t my PDF get any smaller?
The PDF is probably mostly text, fonts and vector graphics, which are already compact, or its images are already compressed. Print-ready files with CMYK colour images may also shrink less. Removing pages or splitting the file are the remaining options.
How do I compress a PDF to under 1 MB or 2 MB?
Try Strong first. If the file is a scan and still too big, use Extreme, which rebuilds pages as roughly 100 dpi images. For long documents, delete unneeded pages or split the file, because a multi-page colour scan may not reach 1 MB while staying readable.
Can I compress a PDF on my iPhone or Android phone?
Yes. Compress PDF runs in mobile Safari and Chrome. Pick the file from Files or Downloads, compress it, and save the result before attaching it to your email.
Is it safe to compress confidential PDFs online?
Many online compressors upload your file to their servers. AnyShift compresses in your browser tab, so the document stays on your device. Only the compressed copy you download is created.