Large PDFs are annoying. They stall email attachments, choke on slow connections, and eat storage. The good news: most PDFs can be compressed 40-70% with almost no visible quality loss — you just need to know what's making them heavy.
What actually makes a PDF big?
Nine times out of ten, it's images. Text is tiny. A page of prose might be 5 KB; a single full-page photo can be 3 MB. Fonts, embedded thumbnails and revision history add up too, but images dominate.
The safe compression checklist
- Downsample images to the resolution you actually need. 150 DPI is plenty for screens; 300 DPI for print.
- Convert photographs to JPEG at 75-85% quality. The eye can't tell.
- Keep line art, screenshots and text-heavy pages as PNG or lossless.
- Strip metadata, thumbnails and unused objects.
Doing it in the browser
Open [Compress PDF](/tools/compress-pdf), drop your file in, pick a quality level, and download. Everything runs locally — no upload, no queue.
When to compress *before* you export
If you control the source, export smart:
- In Word / Docs, use "Save as PDF" with the standard (not print) preset.
- In design tools, flatten transparency and export at screen resolution.
- Crop images before placing them, not after.
Rule of thumb
Aim for under 5 MB for email attachments and under 1 MB for web downloads. If you're still over budget after compressing, split the PDF and send it in parts.
