Gmail’s 25 MB limit, Outlook’s 20 MB default — the quickest way to fail at “just send me the PDF”.
Target: under 10 MB
Even if your mail server allows 25 MB, the recipient’s may be stricter. Target 10 MB for universal compatibility.
Technique 1 — Image downsampling
Images drive 80% of PDF size for most documents. Drop to 150 dpi for screen viewing. Saves 60–80%. First choice.
Technique 2 — JPEG re-encode
Re-encode photographic images with JPEG quality 60–70. Saves another 20–30%. Low risk of visible artefacts on screen.
Technique 3 — Font subsetting
If a document embeds Noto Sans CJK or similar heavy font, subset to used glyphs. Saves 2–10 MB depending on the font.
Technique 4 — Split
Send a single big PDF in two or three chapters. Preserves fidelity. Downside: your reader needs to merge mentally.
Technique 5 — Cloud link
Upload to a secure cloud store and email the link. Zero loss, but the reader may need to click.
Benchmark
A 48 MB construction report was reduced:
- Downsample to 150 dpi → 11.4 MB.
- Downsample + JPEG Q70 → 7.9 MB.
- Downsample + JPEG Q70 + font subset → 7.1 MB.
- Downsample + JPEG Q50 + font subset → 4.6 MB.
Use the Compress PDF tool to apply all three in one click.
Tags: #compress PDF for email #PDF too large #shrink PDF #PDF under 10MB
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