How to Compress a PDF for Email (Without Uploading It)

Why your PDF is too big to email

Most mail services cap the size of a message, attachments included. Gmail, for example, allows up to 25 MB per message (Google's help page), Outlook.com also allows 25 MB (Microsoft's help page), while the Outlook desktop app stops at 20 MB by default for internet mail accounts, and many company mail servers set their own, often lower, limit. Encoding attachments for sending also makes them a little larger than they are on disk, so a file that is just under the limit may still bounce.

What actually makes a PDF heavy is almost always pictures:

• Scanned documents. Every page of a scan is a full-page photo. A ten-page contract scanned on a phone is ten photos, not ten pages of text.
• Photos pasted into reports. Camera images are often stored at their original resolution even when they're printed the size of a stamp.
• Exported presentations and brochures. Design tools tend to embed images at print quality.

Text, on the other hand, takes very little space. That's why the compressor focuses on images.

How to shrink a PDF step by step

1. Open the PDF compressor and choose the PDF tab above the drop area.
2. Drop your file in, or click to pick it. Compression starts right away with the default settings.
3. Look at the result panel: it shows the original size, the compressed size and how many of the embedded photos were recompressed.
4. If the file is still too large, move the Quality slider down. Each change recompresses the file again from the original, so you can go back up at any time.
5. If quality matters less than size, lower Max dimension (px) as well. This scales down large photos inside the PDF.
6. When the size is right, download the new PDF and attach it to your email.

Keep the original. The compressed copy is meant for sending; the original is still the better file to archive or print.

Which settings to choose

The tool has two sliders, and they do different things.

Quality (10-100 %, default 70 %) controls how strongly each embedded JPEG photo is re-encoded. Lower values give smaller files and, at some point, visible blockiness in photos. For a scanned letter or invoice you can usually go quite low before anything becomes hard to read; for a portfolio with photographs you'll want to stay higher. Check the result in a PDF reader before you send it.

Max dimension (px) (400-4000 px, default 1600 px) limits how many pixels the longest side of each photo may have. A scan made at high resolution often has far more pixels than a screen needs. Bringing that down is often the biggest saving, and it keeps photos smooth instead of blocky.

A sensible order: start with the defaults, then lower the max dimension, and only then the quality.

What the compressor does - and what it doesn't

It's worth knowing how the tool works, so the result doesn't surprise you:

• Only the JPEG photos embedded in the PDF are recompressed. Text, fonts and vector graphics are copied unchanged, so text stays sharp and selectable.
• If the PDF contains no photos, the size only shrinks a little, from cleaning up the file's internal structure. The result panel tells you when that's the case.
• Password-protected or damaged PDFs can't be processed. If you know the password, remove it with Unlock PDF first.
• Everything happens in your browser. The file isn't uploaded to a server, there's no account, and no watermark is added.

Still too big? Three alternatives

Split it into parts. If a document is simply long, cut it into two or three files with Split PDF and send them in separate emails. Name them clearly, such as "report-part-1.pdf", so the recipient knows the order.

Send only the pages that matter. Often the recipient needs a few pages, not the whole file. You can pull pages out with the same split tool, or combine just the right pages from several files into one document. Our guide on merging PDF files shows how to pick pages from each file.

Share a link instead. For very large files, upload the original to a cloud drive you already use and email the link. This is the one option where the file does leave your device, so think about who can open the link.

A quick checklist before you hit send

• Open the compressed PDF and scroll through every page. Are signatures, stamps and small print still legible?
• Check the file name. "scan0001.pdf" tells the recipient nothing; "invoice-october.pdf" does.
• Make sure you attached the compressed copy, not the original.
• If the recipient has to print the document, keep the quality a bit higher.

Compressing a PDF for email usually takes less than a minute: drop it into the tool, adjust two sliders, download. Because the work happens on your own device, you don't have to wonder where a confidential contract or a medical letter ends up along the way.