How to Reduce PDF Size for Email Attachments

"Your message couldn't be delivered because the attachment is too large." Most email providers cap attachments around 20–25 MB. Here is how to get a stubborn PDF under the line — without a remote uploader.

Step 1: Compress

Start with the Compress tool at a screen-quality level. For image-heavy or scanned PDFs this often does the whole job, cutting size by half or more. If you want to understand what is happening, see how PDF compression works.

Step 2: Go grayscale

If the document does not need colour, converting to grayscale before compressing removes colour data and shrinks it further. Great for scanned forms and signed paperwork.

Step 3: Split it

Still too big? Split the PDF into two or three parts and send them across separate emails. Practical for large reports where the recipient does not need everything as one file.

Step 4: Strip unnecessary weight

Remove pages you do not need to send with the Remove Pages tool.
Flatten bulky form fields and annotations.

If nothing works

Some documents — large high-resolution photo books, for example — simply cannot shrink below the limit without unacceptable quality loss. In that case share a link via a file service instead. But for the everyday "my scan is 30 MB" problem, compression alone almost always solves it.

Know the limit you're fighting

Most providers cap attachments around 20–25 MB, and the limit applies to the encoded message, so your usable budget is a little lower than the headline figure. Check the size of your file first, then aim comfortably under the cap rather than right at it. Knowing the target turns "make it smaller" into a concrete goal you can hit in one or two steps.

A reliable order of operations

Work from least to most disruptive. Compress at a screen-quality level first, since that alone often clears the limit for scanned documents. If colour is unnecessary, convert to grayscale and compress again. Still over? Remove pages the recipient does not need. Only then consider splitting the document across two emails. Following this order gets you the smallest acceptable file with the least loss of quality.

When a link beats an attachment

Some files genuinely cannot shrink below the limit without unacceptable quality loss — a high-resolution photo book, for instance. Rather than mangling it, share a download link instead. But for the everyday "my scan is 30 MB" problem, compression alone almost always solves it without resorting to a link.

Frequently asked questions

What is the typical email attachment limit?

Around 20–25 MB for most providers, slightly less in practice because of message encoding.

What should I try first?

Compress at a screen-quality level. For scanned PDFs this often gets you under the limit on its own.

How do I shrink it further without losing readability?

Convert to grayscale if colour isn't needed, remove unnecessary pages, then compress again.

What if it still won't fit?

Split the PDF across multiple emails, or share a download link for genuinely large files.

A repeatable recipe for the 'too big to send' problem

The next time an attachment bounces, work a fixed recipe instead of guessing. Check the current size so you know how far you need to travel. Compress at a screen-quality level and re-check — for scanned documents this alone clears the limit most of the time. If you are still over and the document does not need colour, convert to grayscale and compress again. If it is still too big, remove any pages the recipient genuinely does not need. If even that falls short, split the document and send it across two messages, or switch to sharing a download link for files that are simply too large to attach. Working least-disruptive to most means you arrive at the smallest acceptable file with the least loss of quality, and because every step runs locally, none of it requires uploading the document to a size-reducing service first — which would defeat the privacy you presumably wanted by emailing it directly in the first place.

Related guides

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