You scanned a lease with your phone — eight pages, 9.4 MB — and the agency inbox rejected it. Meanwhile a 40-page contract arrives as a 300 KB attachment. Same format, wildly different weight.
This guide diagnoses where your megabytes hide with one number (KB per page), then fixes each cause: oversized scans, bloated decks, and font packing.
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The one-number diagnosis: KB per page
Divide file size by page count. Under 200 KB per page is a normal text document with little fat to trim. Between 200 KB and 1 MB means text plus images or heavy fonts — moderate savings available. Over 1 MB per page means every page is essentially a photograph, and compression works miracles there.
The three usual culprits
Phone scanning apps save each page as a full-resolution 12-megapixel photo — twelve times more pixels than anyone views. Slide decks carry every background and screenshot at original size; a 30-slide deck quietly becomes 25 MB. And quick-export tools sometimes embed entire font families (1–2 MB of typefaces) instead of just used characters.
Scan text documents at 150 DPI instead of 300 — file size quarters with no visible difference on screen. Shrink photos to display size before pasting into Word. Prefer exporters that subset fonts.
Why email bounces 'fitting' files
Attachments travel base64-encoded, inflating them by a third in transit: a 19 MB file becomes ~25 MB of message and bounces off Gmail's 25 MB wall. Outlook allows 20 MB, Exchange defaults to 10 MB. Rule of thumb: aim for 70% of the stated cap.
Steps
- Check KB per page to name the culprit
- Split out only the pages you need
- Compress with the matching preset — or an exact MB target
- Verify the result opens, then send at 70% of the cap
Pro tips
- Merge first, compress second — optimizers dedupe shared resources across the whole file.
- A 600 DPI scan holds sixteen times the data of 150 DPI. Nothing on screen needs 600.
Frequently asked questions
Why is my 2-page PDF 9 MB?
Almost certainly phone-camera pages at full resolution. Re-scan at 150 DPI or compress hard — expect 90%+ reductions on photo-pages.
Will compression ruin my document?
Text reflows losslessly; photos trade pixels for bytes. Lean text PDFs only lose 10–15% because there is little to remove.
The file fits the limit but still bounced. Why?
Base64 transit encoding adds ~33%. A file at 95% of the cap routinely fails — aim for 70%.