How to Compress a PDF to Send by Email

When a PDF is too big to email, compress it before you attach it: open Compress PDF, add the file, choose Balanced, and download the smaller copy. The tool shows the old and new size so you know straight away whether it will fit. Scanned documents and PDFs full of photos usually shrink the most — often by 70–90% — while the text stays sharp.

Email size limits at a glance

Every email service caps the size of a message, and attachments grow by about a third when they're sent, because email encodes them as text. As a rule of thumb, keep a PDF comfortably under these sizes:

The person you're writing to matters too: if their company server accepts only 10 MB, your 18 MB attachment bounces even though Gmail sent it happily.

Compress a PDF in four steps

1. Open Compress PDF on your computer or phone.
2. Add the PDF — drop it on the box or click to choose it.
3. Pick a level: Light keeps the best quality, Balanced suits most documents, and Strong makes the smallest file.
4. Click Compress PDF, compare the sizes, and click Download compressed PDF.

The new file is saved with "-compressed" added to its name, so your original is still there if you need it.

Which compression level?

• Light keeps photos at up to 2,400 pixels. Choose it for brochures, photo reports and anything that might be printed.
• Balanced (up to 1,600 pixels) keeps scanned letters and forms perfectly readable on screen and in print at normal size. It's the right choice nine times out of ten.
• Strong (up to 1,100 pixels, more compression) is for getting under a tight limit. Scanned text is still readable on screen, but photos lose detail when you zoom in.

If Balanced isn't enough, run Strong on the original file rather than compressing the already-compressed copy again.

Why some PDFs barely shrink

PDFs are big for one of two reasons:

1. Photos and scans. A single phone photo can be 3–5 MB, and a scanned page is a photo of paper. These compress dramatically.
2. Text, fonts and drawings. A 200-page report that's all text is already compact; there's little to squeeze.

The tool compresses the photos inside the PDF and leaves text, fonts and vector drawings exactly as they are. If your file is mostly text, it will tell you there's nothing much to compress. Then the options are to send fewer pages — drop the ones you don't need with Remove PDF Pages, or send part of it with Split PDF — or share a link instead (see below).

If it's still too big

• Split it into two emails. Use Split PDF to send pages 1–20 and 21–40 separately.
• Remake it from photos. If the PDF came from phone pictures, rebuild it with Image to PDF and keep Make the PDF smaller ticked — it scales photos down as the PDF is made.
• Share a link. Gmail offers to send large files as a Google Drive link, Outlook as a OneDrive link, and Apple Mail can use Mail Drop. The recipient downloads the file from the link instead of receiving it as an attachment.

Does compression change my document?

Only the photos inside it. Each picture is scaled down to the level's size and saved with more compression, and it's only replaced when that genuinely saves space. Text stays selectable and searchable, links keep working, and the page count and layout don't change. Look through the compressed file before you send anything that has to be printed at high quality.

Frequently asked questions

Is it safe to compress confidential PDFs?

Yes. Compression runs in your browser; the PDF isn't uploaded to a server. That makes it suitable for payslips, contracts, medical letters and ID scans.

Can I compress a PDF on my phone?

Yes — the tool works in Safari on iPhone and in Chrome on Android. The compressed copy goes to your Downloads folder, ready to attach in the Mail or Gmail app.

Why does it say the PDF is password-protected?

Encrypted PDFs can't be rewritten until the password is removed. If you know it, unlock the file with Unlock PDF, then compress the unlocked copy.