PDF Too Large to Email? Here Is How to Send It

Two things work against you. First, the limit applies to the entire message: the body, your signature, inline images, headers and every attachment together. Second, attachments travel as text. Base64 encoding turns three bytes into four characters, which inflates the file by about 33%, and line breaks push it closer to 40%.

So a 24 MB PDF arrives at the server as roughly 32 MB and is refused by a 25 MB rule. As a rule of thumb, the largest file you can actually attach is about three quarters of the published limit.

• Gmail and Yahoo publish 25 MB, which leaves room for a file of about 18 MB.
• Outlook.com and iCloud Mail publish 20 MB, so plan for about 14 MB.
• Company Exchange servers are often capped at 10 MB, and the administrator can set anything.
• The recipient has a limit too, and it is the smaller of the two that decides.

Aim for 10 MB. It passes every common inbox with room for the message itself, it survives a stricter server on the other side, and a scanned document still looks fine at that size. If you know the recipient is on a corporate server, 5 MB is safer still.

Do not compress further than you need. Every step down costs image quality, and a target size lets you stop at exactly the limit instead of guessing.

Preview can shrink a PDF: open it, choose File > Export, pick Reduce File Size from the Quartz Filter menu and save. It costs nothing and sometimes it is enough.

What it cannot do is aim. The filter applies one fixed recipe to every document, so a heavy scan often stays above the limit while a light one comes back blurry, and you have no way to say "under 10 MB". Doing it for twenty files, one at a time, is its own punishment.

In File Acture, open Compress PDF, set Compress by to Target size and type 10 MB. The app re-encodes only the images, trying resolutions from 300 down to 72 DPI and a range of JPEG qualities until the real file size fits your number. Text, fonts and vector drawings are never touched, so the document stays sharp and searchable.

In a test on an Apple M4, a 54 MB scan of 36 pages reached a 5 MB target in 1.38 seconds and came out at 4.84 MB. If a file already fits, it is left alone rather than re-encoded, and if your target is impossible, the app tells you the smallest size it can reach instead of saving a ruined copy.

Everything happens on your Mac. A contract, a payslip or an ID scan never leaves the machine, which matters more for the documents you email than for anything else.

Often the PDF is not the problem: three phone photos pasted into the message can outweigh it. iPhone photos are large, and a screenshot on a Retina display is bigger than it looks.

Compress the images to a target in KB first, or put them into a single PDF so the whole set travels as one small file.