How to Compress a PDF to Fit Email and Upload Limits

"The attachment is too large." "Maximum file size: 2 MB." PDFs full of scans or photos hit these limits all the time, and the fix is usually compression.

The important thing to understand is what makes your PDF big, because that decides which setting to use.

What makes a PDF heavy

• Scans and phone photos. A scanned page is a full-page image. Twenty of them at high resolution can easily be 30 MB.
• Embedded photos in brochures, portfolios and reports.
• Fonts add a little. Usually not the problem.
• Plain text is tiny. A 100-page text-only PDF might be under 1 MB.

So if your PDF is big, it's almost always images. That's where compression helps.

The three levels

• Lossless, keeps text selectable. Repacks the file without touching its content. Safe, modest savings. Best for text documents.
• Balanced, good quality, much smaller. Re-renders each page as an optimised image. Big savings on scans and photo-heavy PDFs.
• Strong, smallest file. Same approach as Balanced, pushed harder. For strict limits.

Balanced and Strong make the text unselectable, since each page becomes an image. For scans that doesn't matter (they were images anyway). For a contract someone needs to copy from, use Lossless.

How to compress a PDF with ZapMorph

1. Open Compress PDF

Go to the Compress PDF tool.

2. Add the PDF and choose a level

Drop in your PDF and pick Compression. Start with Balanced.

3. Compress and download

Click Compress PDF. The result shows the new size. If it isn't smaller than the original, you get the original back, so you'll never end up with a bigger file.

Still too big?

1. Try Strong.
2. Split it: send it in two parts with Split PDF or Extract PDF Pages.
3. Remove pages nobody needs (blank backs, cover sheets) with Remove PDF Pages.
4. Go grayscale. Color scans are heavier. Grayscale PDF can help when color doesn't matter.
5. Re-scan at a lower DPI. 150–200 DPI is plenty for documents. 600 DPI is overkill.

Other ways

• Mac Preview: File → Export, Quartz Filter Reduce File Size. It's aggressive and can make scans very blurry.
• Adobe Acrobat: Reduce File Size or Optimize PDF. Excellent control, paid.
• Word/PowerPoint exports: choose "Minimum size" or compress pictures before exporting to PDF.

Which level for which PDF

If it's still too big

1. Split it with Split PDF and send parts.
2. Remove pages you don't need with Remove PDF Pages.
3. Grayscale it: colour scans are bigger. Black and white can help.

Summary

Big PDFs are big because of images. Start with Balanced in Compress PDF, keep Lossless for text documents that need to stay selectable, and reach for Strong only when you must.