The short answer
Compress the PDF so it’s comfortably under your email provider’s limit. For a 25 MB cap, aim for under 18 MB, because attachments grow by about a third on the way. If the quality can’t change at all, split the file into parts instead.
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Step by step
- Find out the real limit Gmail and most Microsoft 365 mailboxes stop at 25 MB. Outlook.com and iCloud stop at 20 MB, and lots of company mail systems at 10 MB. Aim below the limit, not right at it.
- Compress to a target Open Compress PDF, type the size you need and run it. Scans and photo-heavy reports usually shrink by 80–95% without any visible difference.
- Look at the before-and-after You’ll see the old and new version of a page side by side with a slider between them, plus a score for how much changed. Check the page with the smallest print.
- If it still will not fit, split it Split by size fills each part to just under the limit, so you send as few attachments as possible. Say "1 of 3" and so on in the email so the other person knows they have everything.
- Attach and send What you get is a normal PDF: same pages, same order, and the text can still be selected and searched.
Questions
Why did a 24 MB file bounce from a 25 MB limit?
Email encodes attachments to send them, and that adds roughly a third to the size. For a 25 MB limit, keep the file under about 18 MB.
Does zipping help?
Hardly at all, because a PDF is already compressed inside. Zip is useful for bundling several files into one attachment, not for shrinking one.
Will the recipient notice the compression?
On a mostly-text document, no, because the text isn’t touched. On a file full of photos, look at the preview at your target size before you send it.
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