How to reduce PDF file size

Hitting a 5 MB email limit or an upload cap? Here are the practical ways to shrink a PDF — and how to do it without handing your file to a server.

Why PDFs get large

Most oversized PDFs are heavy for one reason: images. A document scanned at high resolution, or one full of photos and screenshots, carries far more data than a text-only file. Fonts, embedded thumbnails and saved editing history add smaller amounts on top. Shrinking a PDF is mostly about reducing the size of the images inside it.

The most effective methods

1. Lower the image resolution. A scan at 600 DPI looks identical to 150 DPI on screen but is many times larger. Re-scanning or re-exporting at 150–200 DPI is the single biggest win.
2. Convert pages to compressed images. If you only need the document to be viewed (not edited or searched), turning pages into JPGs and rebuilding the PDF drops the size sharply.
3. Remove pages you don't need. Fewer pages, smaller file. Extract just the pages that matter.
4. Flatten and re-save. Re-saving a PDF often discards redundant data left behind by editors.

A quick private workflow with meldpdf

Everything below runs in your browser — your file is never uploaded:

• Convert the PDF to JPG at Standard quality — this compresses the images.
• Turn those JPGs back into a PDF — the result is usually much smaller.
• Need only a few pages? Extract them first so you're not compressing the whole document.

This "view-only" approach trades editability for size, and is perfect when you just need to email or upload a document.

When not to compress

If the reader needs to select text, run OCR, or fill form fields, avoid converting to images — you'll lose that. In those cases, re-export at a lower DPI from the original source instead.

Frequently asked questions

What's a good target size for email?

Most email providers allow 20–25 MB, but many company systems cap attachments at 5–10 MB. Aiming under 5 MB is the safe bet.

Does compressing lose quality?

Image-based compression reduces image detail slightly. For on-screen reading it's usually unnoticeable; for print, keep resolution higher.

Is my file uploaded?

No. Every meldpdf tool runs locally in your browser. See our privacy policy.