The short answer
Compress the PDF toward a target comfortably below your email provider’s attachment limit — not right up against it — before you attach it. Compress a PDF for email now, or read on for the actual limits and why “just under the limit” isn’t always safe.
The real limits (and why they’re not the whole story)
Google’s Gmail help gives a 25 MB attachment limit for personal accounts; anything larger is automatically replaced with a Google Drive link. Microsoft’s Outlook help lists a 20 MB limit for Outlook.com and Gmail accounts used in Outlook, and a 10 MB default for work (Exchange) accounts. Work and school administrators can set their own limits, so the inbox you’re sending to may accept less than yours.
Here’s the part that catches people out: email attachments aren’t sent as raw bytes. They’re encoded (typically Base64) for sending, which inflates the file by roughly a third, so a 20 MB attachment becomes closer to 27 MB. A file that looks like it’s just under your provider’s stated limit can still be rejected once encoding overhead is added. The practical fix is simple: aim well under the limit, not right at it.
How to reduce a PDF for email
- Open the PDF compressor and add your file.
- Pick a target size well below your actual limit — for a 25 MB Gmail cap, targeting 10–15 MB leaves real headroom; for a stricter 10 MB organizational limit, target 5–7 MB.
- Compress and check the real result size before attaching anything.
- Download and attach the compressed file.
If you’re regularly sending several documents together, compress them all to the same target at once rather than repeating this one file at a time.
Why the file got big in the first place
Scanned pages, high-resolution photos, and PDFs exported straight from design tools are the usual culprits — a handful of full-resolution images can dwarf a whole document’s worth of text. If you’re not sure why a particular file is large, see the common causes before deciding how aggressively to compress it.
An example
A scanned three-page government form, saved straight off a scanner at default settings, can easily run 8–12 MB. Add a signed cover letter and another attachment to the same message, and you’re already close to a 20 MB Outlook.com limit. Compressing that scan toward a 2–3 MB target usually keeps it legible and leaves plenty of room under the limit.
FAQ
Do all email providers use the same size limit?
No. Gmail and Outlook.com differ, and work or school accounts follow whatever limit their administrator sets; Microsoft’s default for Exchange accounts is 10 MB. If you’re emailing into an organization you don’t control, you can’t know its limit in advance, so a smaller file is the safer choice.
I’m sending several PDFs in the same email — does each need to fit the limit separately?
No — the limit applies to the whole message, all attachments combined, not each file individually. If you’re attaching multiple documents, compress them all to a shared target at once so the total stays under your limit, rather than compressing each one to the full limit and going over when combined.
Is a compressed PDF less trustworthy for something like a signed contract?
Its wording doesn’t change. A text-based contract is usually just repacked, with no visible change to the pages. One catch: if the contract carries a certified digital signature (the kind a PDF reader reports as valid), compressing rewrites the file and that signature will stop validating. Compress before signing, or send the signed original another way. A scanned or drawn signature is just an image and stays on the page.