How to Compress a PDF for Email (and Stay Under the Size Limit)

You've finished a report, a set of scanned forms or a signed contract, you press send, and the email comes back with "attachment too large". It happens most often with scanned documents and PDFs full of photos, and the fix is usually quick once you know what the limit really is and which lever to pull.

The size limits you are working with

Every email service caps how much you can attach to a single message. These are the published limits for personal accounts at the time of writing:

Sources: Gmail Help, Microsoft Support and Yahoo Help. Work and school accounts are different: an administrator sets the limit, and it is often lower.

Two details catch people out. First, the limit is for the whole message, so three 9 MB attachments fail just like one 27 MB file. Second, the recipient's service has a limit too. A 24 MB file might leave Gmail happily and still bounce at an office mail server that accepts 10 MB.

Leave headroom

Attachments are converted to plain text for the journey, an encoding called Base64, and that makes them roughly a third larger in transit. A PDF that is 19 MB on your computer can arrive at a mail server as something close to 25 MB. That is why a file that looks just under the limit sometimes fails anyway.

A practical rule: aim for 15 MB or less for Gmail and Yahoo, and 10 MB or less when you don't know what the recipient uses. Portals for job applications, visas and university admissions are often stricter still, commonly 2 to 5 MB per file, so check the upload page before you start.

Check how big the file really is

Before changing anything, look at the exact size:

• Windows: right-click the file, choose Properties and read Size.
• Mac: select the file and press Command + I.
• Android and iPhone: open the file in your Files app and tap the info or details button.

Write the number down. It tells you how much you need to save, and it lets you judge whether the compressed version is worth it.

Option 1: Compress the PDF

For most oversized PDFs this is the only step you need. Open the PDF compressor, add the file, and start with the default settings. The size before and after appears on screen, so you know straight away whether you're under your target.

The tool offers two approaches, and choosing the right one matters:

• Keep text sharp shrinks the pictures inside the document and leaves the text alone. Choose this for anything the recipient may need to search, copy from or fill in: reports, invoices, contracts, CVs.
• Maximum compression redraws every page as an image. It gives the biggest savings on scans and photographed pages, but the text can no longer be selected or searched and links stop working. That is usually fine for a scanned ID card or a signed form, and not fine for a document someone needs to edit.

If the first attempt isn't small enough, move one level stronger and compare. Zoom in on the result before you send it, especially on small print, stamps and signatures, which are the first things to blur.

Everything happens inside your browser, so confidential paperwork isn't uploaded anywhere while you do this.

Option 2: Split it into parts

Some documents are simply big: a 300-page manual, a year of bank statements, a portfolio full of high-resolution artwork. If compression alone can't bring them down far enough, send the document in parts.

Use Split PDF to cut the file into ranges that make sense to the reader, such as one part per chapter or per month, rather than arbitrary chunks. Then send them as separate emails numbered in the subject line: "Annual report (1 of 3)", "(2 of 3)" and so on. Numbering stops the recipient from wondering whether a part went missing.

Splitting also helps when a portal accepts several small files but refuses one large one.

Option 3: Combine first, then compress

The opposite problem is just as common: ten separate scans, each small enough, but together far over the limit, and a recipient who would rather not open ten attachments.

Join them with Merge PDF in the order the reader expects, then run the single combined file through the compressor. You get one tidy attachment, and compressing one file usually saves more than compressing ten small ones, because the same settings are applied across the whole document.

When to send a link instead

If a file is still over the limit after compression, or it's something like a print-ready brochure where you don't want to lose any quality, a cloud link is the honest answer. Gmail does this automatically with Google Drive above 25 MB, and Outlook users can share from OneDrive. Remember that a link means the file now lives on that service, so check the sharing setting (anyone with the link, or named people only) before you send it.

Why zipping a PDF barely helps

It's tempting to right-click and make a ZIP file. With PDFs the saving is usually tiny, often just a few percent, because the contents of a PDF are already compressed internally. A ZIP also adds a step for the recipient and is blocked by some company mail filters. Compressing the PDF itself works far better.

Make smaller PDFs from the start

If you scan documents regularly, a few settings prevent the problem entirely:

1. Scan text documents at 150 to 200 DPI. That is plenty for reading and printing. 600 DPI produces files many times larger with no visible benefit on a screen.
2. Use greyscale or black and white for letters, forms and receipts. Full colour is only needed for photos, stamps or coloured charts.
3. Crop to the page. Phone scanning apps often capture the table around the paper, which adds size and looks untidy.
4. Export, don't print to PDF, from office software, and pick a "smaller file" or "online" option if it offers one. Printing to PDF sometimes embeds images at full resolution.

A quick checklist before you press send

• The file is comfortably under the limit, ideally 15 MB or less for Gmail and Yahoo.
• The compressed version has been opened and checked, especially signatures and small print.
• Documents the recipient needs to search or edit still have selectable text.
• Multi-part sends are numbered, and one message explains how many are coming.
• The file name says what it is: Invoice-2026-041.pdf beats scan0003.pdf.

A few minutes of preparation saves the back-and-forth of bounced emails and "the attachment didn't come through" replies, and it keeps your document looking the way you intended.