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How to make a PDF small enough to email

Last updated: 28 October 2026

You try to email a PDF and get “attachment too large”, or the message bounces. Most email services cap attachments at around 20–25 MB per message, and a single scanned contract or a presentation exported to PDF can easily go over that. The good news is that most oversized PDFs can be made several times smaller without any visible change.

Email size limits

Common limits are 25 MB per message in Gmail and Yahoo Mail and 20 MB in Outlook.com and many company mail servers. Gmail offers to send larger files as a Google Drive link instead.

One detail catches many people out: attachments are encoded as text while they travel, which makes them about a third larger. A 19 MB PDF can therefore be rejected by a 25 MB limit. To be safe, aim for under about 15 MB for the whole email, and under 10 MB if you do not know the recipient’s mail system.

Why the PDF is so big

Text in a PDF is stored as characters and fonts and takes very little space: a 50-page report made in a word processor is often under 1 MB. What makes PDFs heavy is pictures:

  • Scans and phone scans, where every page is a full-resolution photo of paper;
  • Photos placed in documents, often straight from a camera at 12 megapixels or more;
  • Presentations exported to PDF, which keep every slide image at its original size.

A screen or an office printer cannot show anywhere near that much detail, so those images can be saved at a sensible size and still look the same.

Compress the PDF

The Compress PDF tool does exactly that. It re-saves the images inside the PDF at a lower resolution and leaves text, links and page layout untouched:

  1. Drop the PDF into the tool or click Choose files.
  2. Start with the Recommended level. It typically saves 50–80% on scanned and photo-heavy files while the pages stay sharp on screen and in print.
  3. Check the new size next to the file. If it is still too big, choose Strong, which goes further and is still fine for reading on screen.
  4. Download the smaller PDF and attach it.

The file is processed in your browser and never uploaded, which matters for the documents people most often email: contracts, bank statements, medical letters and ID scans.

If the tool says it kept the original, the PDF has no large images to shrink. That is usually the case for invoices and documents generated by software, which are already small.

Still too big? Split it

A very long scan can stay too large even after compression. In that case, use Split PDF to cut it into parts, for example pages 1–20 and 21–40, and send them in separate emails. Or send only the pages the recipient actually needs.

Avoid the problem next time

  • When scanning, choose 150–200 DPI for documents you will read on screen. 300 DPI and colour are only needed for photos or documents that will be printed professionally.
  • In Microsoft Word, choose File → Save As → PDF and set Optimize for to Minimum size (publishing online).
  • Shrink large photos before placing them in a document, for example with Resize Image.

Tools used in this guide

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