A 40 MB PDF that won't attach to an email is almost always fixable in minutes. Here's how to diagnose what's bloating your file and shrink it with six free methods — no uploads, no sign-up.
Compressing blindly wastes time. PDFs get huge for a handful of reasons, and the right fix depends on which one applies:
The #1 cause. Scanned pages and photos at 300+ DPI multiply file size. If your PDF is mostly images, image compression is the fix.
Virtual printers often rasterize pages into images — even for plain text. A native Export as PDF keeps text as text and stays small.
Full font files embedded for every typeface add megabytes. Subsetting or standard fonts shrink this overhead.
Comments, annotations, form data, edit history and metadata quietly inflate size — sometimes by 10–20%.
Knowing your PDF type saves you from compressing the wrong thing:
Every page is already an image. Compression works brilliantly here — expect big savings, but the text was never selectable to begin with.
Usually already small. If one is huge, suspect embedded fonts, hi-res logos or print-to-PDF rasterization. Image recompression barely helps — and can make the file bigger.
This is why most people end up here — the file won't attach. Common limits:
25 MB per message (including encoding overhead, so aim for ~20 MB).
Around 20 MB for Outlook.com; 10–35 MB on work/school accounts depending on admin settings.
Often stricter — 5–10 MB is common. Compress first, then check the portal's stated limit.
If your PDF is over 20 MB, assume it will fail somewhere. Get it under 10 MB and it attaches virtually everywhere.
You can't always do both — but you can get close. Start with zero-quality-loss wins: remove unnecessary pages and strip metadata. Then downsample images to 100–150 DPI, which stays perfectly readable on screen. Only recompress aggressively if you can accept softer text.
Almost always images: scanned pages, high-resolution photos, or a file printed to PDF at 300+ DPI. Embedded fonts, annotations and hidden metadata add smaller but real overhead.
Yes for the lossless parts: removing pages, stripping metadata and subsetting fonts never touch visual quality. Image downsampling is lossy, but 100–150 DPI keeps documents perfectly readable on screen.
Yes — this is usually the biggest lever. A PDF built from 300 DPI scans can shrink 60–80% by re-rendering pages at 100 DPI. The trade-off is that fine print gets softer.
Yes. This site's compress tool runs entirely in your browser — your PDF never leaves your computer, which also makes it safe for confidential documents.
It can, especially in long documents that embed full font files. When exporting, choose standard fonts or font subsetting so only the characters used are stored.
Metadata alone is small, but PDFs also carry hidden extras: comments, annotations, form data and edit history. Stripping these typically saves 5–20% — worth it when every megabyte counts.
Desktop tools like Adobe Acrobat Pro offer batch processing. In a browser, the fastest approach is to merge the PDFs first, compress once, and then split the result back into separate files if needed.