How to reduce a PDF's file size for email

How small does it need to be?

Check the limit before you start, because it decides how hard you need to compress. These are the published limits for the two biggest personal email services:

Leave some headroom. Email sends attachments encoded as text, which makes them roughly a third larger on the way, and the person receiving it may have a lower limit than you. For a 25 MB limit, aiming for 15 MB or less is a safe target. Upload portals often set much smaller limits, like 2 MB or 5 MB, so read the form.

Find out why the PDF is big

Text and vector drawings take up very little space. Almost every oversized PDF is big because of images:

• Scanned pages. Each page is a photo of paper. If you can’t select the words with your cursor, it’s a scan.
• Photos at camera size. A report or brochure with phone photos dropped in at full resolution.
• Pages exported as images. Some apps “print” every page as a picture, even plain text.

A quick check is to divide the file size by the number of pages. A 12-page file of 36 MB is 3 MB a page, which is images, not text. A 40-page text document that is already 1 MB won’t get much smaller, and that’s fine.

Compress it without uploading

Most online compressors upload your file to their server, process it there and send it back. That’s a problem for anything personal. A tool that runs in the browser does the same work on your own device.

1. Open Compress PDF and add the file. Drop it on the page or choose it from your files. It works on a phone too.
2. Let it re-compress the images. Photos and scanned pages are saved again at a lower quality. Real text stays as text, so it stays sharp and searchable.
3. Check the result before sending. Open the smaller file and zoom into the smallest print, a signature or a stamp. If anything is hard to read, use a lighter setting.

You can check that nothing is uploaded: once the page has loaded, turn on airplane mode and run it again. A tool that really works locally keeps working.

Send only the pages they need

A landlord who asked for your last two payslips doesn’t need the 30-page bank statement they came with. Use Extract PDF pages to save just the pages that matter as a new file. It is often the biggest saving of all, and the recipient will thank you.

If every page is needed and the file is still too big, Split PDF cuts it into parts that you can send in separate emails. Name them clearly (“Lease part 1 of 2”) so nothing gets missed. Splitting doesn’t make the total smaller. It only spreads it out.

If you are scanning, fix it at the source

Rescanning with better settings usually beats compressing a bad scan:

• Use grayscale or black and white for text documents. Colour is only worth it for photos, stamps or highlighting that matters.
• Pick a sensible resolution. 150 to 200 dpi is readable on screen. 300 dpi is the usual choice if the document will be printed. Higher settings mostly add size.
• Use document mode on phone scanner apps, which crops to the page and flattens the background, instead of saving full-colour photos.

When a PDF won’t get much smaller

If compression only saves a little, the file is probably already efficient: mostly text, or images that were compressed once already. Compressing again only makes those images worse. Your options then are to send fewer pages, split the file, or share a link through Google Drive or OneDrive instead of attaching it. Gmail does this for you above 25 MB, and in Outlook.com you can attach a OneDrive link instead of the file.

Sources

• Gmail Help: Attachment size limits. 25 MB for personal accounts, Drive link above that
• Microsoft Support: Unable to attach files in Outlook.com. 25 MB per email including text, OneDrive links