PDF Guides
PDF Too Large to Email? Attachment Limits and Fixes (UK and Australia)
You attach a signed lease, a set of accounts or a job application and the email fails, or worse, it seems to send but never arrives. Attachment limits are one of the most common reasons. The limits are not the same everywhere, and the size of your file is not always the size the mail system counts.
The limits you are working with
Gmail allows messages up to 25 MB, and larger files are typically replaced by a Google Drive link. Microsoft documents a 20 MB limit for internet email accounts such as Outlook.com, and some guidance mentions 25 MB, so the safe assumption is that 20 MB is the practical ceiling when you are unsure. Company, university and government mail systems are configured by their administrators and can be lower still, which you usually only discover when a message is bounced.
Why your file counts for more than its size
Email attachments are encoded for transport, which makes them larger than the file on your disk. As a rough guide, a file of around 18 MB can end up close to a 25 MB limit once encoded. If you are near the ceiling, assume it will not fit and trim it down. Several attachments add up, so three moderate files can exceed a limit that each one is under.
Shrink the file first
The quickest fix is to compress the PDF. Scanned documents and files with photos benefit most, while text-based PDFs are usually already small. Compress gradually and zoom in to confirm that small print, signatures and figures are still legible. This matters for contracts and financial documents, where clarity is essential.
- Compress the PDF and check it is still readable
- Remove pages you do not need to send
- Split very large files into parts that fit the limit
- Send several smaller emails if the recipient prefers it
Split when compression is not enough
If a document is genuinely large, use the split by size tool to divide it into parts that each stay under a limit you choose, and say in your email how many parts to expect. Labelling files clearly, for example part one of three, saves the recipient from guessing. You can also remove pages the recipient does not need with the remove pages tool.
When a link is better than an attachment
For very large files, a shared link from a cloud storage service is often more reliable than an attachment. Be careful with sensitive documents: use access controls, and consider adding a password with the protect PDF tool. If the recipient has told you their preferred method, use that.
Avoiding problems next time
If you regularly send large documents, ask the recipient what size they can accept before you start. It costs one short message and saves a failed submission on a tight deadline.
Where you can, send files earlier than you need to. That leaves room for a bounce or a request to resend in a different form, and it means a deadline is never lost to a technical limit you did not know about.
Frequently asked questions
What is the attachment limit for Gmail and Outlook?
Gmail allows up to 25 MB per message. For Outlook.com and other internet accounts Microsoft documents 20 MB, so treat 20 MB as the safe limit.
Why did my email bounce with a file under the limit?
Attachments grow when encoded for email, several files add together, and the recipient's mail system may have a lower limit than yours.
How do I make a scanned PDF smaller?
Use the compress PDF tool, then zoom in to check the text is still readable. Scanned pages usually shrink the most.
Does the tool upload my file?
No. Compressing and splitting happen in your browser, so your file stays on your device.
How can I tell if my email was delivered?
Ask the recipient to confirm receipt for anything important, and watch for bounce messages in your inbox.