How to reduce PDF file size
To reduce a PDF's file size, open the Compress PDF tool, add your file, and choose either a quality level or an exact target size — PDFER re-encodes the document in your browser and downloads a smaller copy. Nothing is uploaded, so even large, confidential files stay on your device.
Why PDFs get large
Most oversized PDFs are heavy because of images — high-resolution scans or photos embedded at full resolution. Fonts, duplicated objects, and uncompressed page streams add to it, but images dominate.
That is why the biggest savings come from re-rendering pages at a sensible resolution and re-compressing images, rather than from tweaking metadata.
Compress by quality level
The Light level losslessly repacks the file (dedupes objects, packs streams) and keeps text fully selectable — a safe first try.
Recommended and Smallest re-render each page as an image at a lower DPI and JPEG quality. They shrink the file the most, but the page becomes an image, so its text is no longer selectable.
Compress to a target size
If you need to hit a limit — say an upload cap or an email attachment size — switch Compress PDF to “To target size” and enter a number in KB.
PDFER tries progressively stronger settings and stops at the best-looking version that fits under your target. If the target is very small, you get the smallest version it can produce.
Tools mentioned in this guide
Frequently asked
- Does compressing a PDF reduce quality?
- Lossless (Light) compression does not change how the document looks. Stronger levels re-render pages as images at a lower resolution, which reduces quality in exchange for a much smaller file.
- Is there a file-size limit?
- No server limit — compression runs in your browser, so the only ceiling is your device's memory. Nothing is uploaded.