How to send a PDF that's too big to email
An attachment that looks comfortably under the limit can still be rejected, and the reason is rarely the one people assume.
Your file is bigger on the wire than on disk
Email attachments are not sent as raw bytes. They are encoded first, and that encoding adds roughly a third to the size. A 20 MB PDF arrives at the server as about 27 MB, which is why a file that looks safely under a 25 MB limit gets bounced anyway.
The limits themselves vary more than you would expect. Gmail stops at 25 MB, Outlook.com at 20 MB, and corporate mail servers are frequently configured at 10 MB — and the *recipient's* limit matters as much as yours. A message can leave your outbox and be rejected two hops later.
Find out what's making it heavy first
A hundred-page contract that was typed is usually under 2 MB. A three-page scan of the same contract can be 40 MB. The difference is that the scan is not text at all — it is three large photographs of paper, and the page count tells you nothing about the weight.
This matters because the fix is different in each case. A scan responds dramatically to compression. A text PDF that is already 8 MB is probably carrying embedded fonts and full-resolution images that compression will barely touch, and needs splitting instead.
Option one: compress it
This is the right first move for anything scanned or image-heavy, and it routinely cuts a 40 MB scan to under 5 MB with no visible difference on screen. Compression is lossy at the stronger settings, so keep your original — but for something that is going to be read rather than reprinted, the loss is invisible.
If the result is still too large, the document probably needs to be smaller in pages, not in bytes.
Option two: split it
Two 8 MB emails always work where one 16 MB email does not. Splitting a PDF into parts is unglamorous and completely reliable, and it has the side benefit of letting the recipient open part one while part two is still arriving.
If only some of the document is actually needed, extracting those pages is better still — a smaller file and less for the other person to wade through.
What doesn't work
- Zipping a PDF. PDFs are already compressed internally, so a ZIP typically saves two or three percent and adds a step for the recipient.
- Renaming the extension to get past a filter. The mail server reads the file's signature, not its name.
- Sending it twice. If it bounced on size, it will bounce again.
When nothing fits
Past a certain size, email is the wrong channel and no amount of compression changes that. Put the file in shared storage and send a link. Before you do, it is worth stripping the document's metadata: PDFs routinely carry the author's name and internal working titles, and a link is often shared further than an attachment.