PDF guide

How to reduce a PDF's file size for email

You try to attach a PDF and your email service refuses it, or quietly swaps it for a cloud link. Most email providers cap attachments at 20 to 25 MB, and a scanned contract, a portfolio or a brochure full of photos can easily go over that.

The good news is that most of a big PDF's size usually comes from the images inside it. Shrink those and the file gets much smaller, while the text stays exactly as it was. Here's how to do that without uploading the document, and how much smaller it needs to be.

Open Compress PDFFree · Runs in your browser · Nothing uploaded

Updated 4 min read

01Step by step

Compress a PDF in your browser

  1. Step 1: Open Compress PDF

    Open Compress PDF in a modern browser, on a computer or a phone.

  2. Step 2: Add the PDF

    Drop the file onto the page or click to choose it. Files can be up to 50 MB. Your browser opens the PDF itself; it isn't sent anywhere.

  3. Step 3: Pick a compression level

    Balanced is the default and the best fit for email: images keep up to 1,600 pixels on their longest side, which looks sharp on screen and prints fine. Choose Light if the file will be printed at high quality, or Strong for the smallest file when photos and scans can look a little softer.

  4. Step 4: Compress and download

    Press Compress. You'll see the original size, the new size and how much you saved. Download the smaller PDF and attach it to your email.

Open Compress PDFFree · Runs in your browser · Nothing uploaded

02Limits

How big can an email attachment be?

Each provider sets its own limit. These are the figures in their help pages as of November 2026:

  • Gmail: 25 MB. If your attachments add up to more, Gmail replaces them with a Google Drive link.
  • Outlook.com: 25 MB per file, though some Outlook apps use a 20 MB limit. Bigger files can be shared as OneDrive links.
  • Yahoo Mail: 25 MB for all the attachments in one message.
  • iCloud Mail: 20 MB per message, or up to 5 GB with Mail Drop turned on.
  • Work and school email: set by your organization, so ask your IT team if you're not sure.

There's one catch. Email sends attachments as text, using an encoding called Base64, which makes them larger on the way. Microsoft's Exchange documentation puts the increase at about 33%. Depending on the service, the limit may apply to that larger size, so a 20 MB PDF can bump into a 25 MB limit. For a 25 MB limit, a PDF of 15 MB or less is a comfortable target.

03Troubleshooting

When a PDF won't get much smaller

Compress PDF works on the images inside a document. If your PDF is mostly text, or its images are already small and well compressed, there's little left to remove, and the tool tells you so rather than handing you a file that isn't any smaller. A few things to try:

  • Try Strong. It shrinks images further, at some cost to their quality.
  • Remove pages you don't need. Organize PDF lets you delete blank, duplicate or unneeded pages before you compress.
  • Split it. Send the document in parts with Split PDF, for example by chapter or page range, across two emails.
  • Scanned in black and white? Black-and-white scans and CMYK print images are left as they are, so they may not shrink much. If you can scan again, a lower resolution such as 150 to 200 DPI is usually plenty for reading on screen.
  • Share a link instead. For very large files, use your provider's own option (Google Drive in Gmail, OneDrive in Outlook, Mail Drop in Apple Mail) or a cloud drive you trust.

04Alternatives

Other ways to shrink a PDF

On a Mac: Preview

Open the PDF in Preview, choose File > Export, pick Reduce File Size from the Quartz Filter menu and save. It's quick, but Apple notes the result may be lower in quality, so check images and scans before you send it.

When you create the PDF

If you're making the PDF yourself, export it at a smaller size in the first place. In Microsoft Word for Windows, for example, the Save As PDF options let you choose Minimum size (publishing online) instead of Standard. Scanning apps usually have a quality or resolution setting too.

Online compressors

Many websites compress PDFs by uploading them to their servers, processing them there and deleting them after a while. That's fine for a public brochure, but think twice before uploading contracts, bank statements, ID scans or medical letters. See how UtilOrb compares with iLovePDF and Smallpdf.

05FAQ

Questions people ask

No. Only the images are re-saved. Text, fonts and vector graphics are left exactly as they were, so they stay crisp at any zoom and you can still select, search and copy the text.

Comfortably below your provider's limit, because attachments grow by roughly a third when they're encoded for sending. For a 25 MB limit, 15 MB or less is a safe target. Smaller files are also quicker for the person receiving them to download.

It depends on where the work happens. Most online compressors upload your document to their servers. UtilOrb's Compress PDF runs in your browser tab, so the file never leaves your device and there's nothing to delete afterwards.

Compress PDF handles one file at a time. Compress each one in turn, or combine them first with Merge PDF and compress the merged file.

Try it now

Ready? Open Compress PDF.

It's free, there's nothing to install, and your files stay on your device the whole time.

Open Compress PDFFree · Runs in your browser · Nothing uploaded

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