This tool actually shrinks your PDF's file size, rather than just re-saving it with a smaller number attached. It works by finding every embedded image inside the PDF, downsampling it to a target resolution, and re-encoding it at a chosen quality level, the same category of technique desktop compression software uses, running fully in your browser via pdf.js and an image-recompression pipeline.
There are five presets, Minimal, Light, Recommended, Strong, and Extreme, trading off quality against file size, plus a Target Size mode where you type an exact goal like "500 KB" and the tool searches across quality and resolution settings to get as close as it can, honestly reporting if a particular target genuinely isn't reachable rather than pretending to hit it. On a typical image-heavy scanned PDF, the Recommended preset alone can cut file size by more than half; more aggressive presets go further at the cost of visible image quality.
Because compression happens entirely on-device, nothing is uploaded, it also means there's no file-size ceiling imposed by a server upload limit, and no watermark. The tool shows your original size, the new size, and the percentage saved side by side, plus a visual preview of page one before and after, so you can see exactly what a given preset does before committing to it. If a compressed result somehow comes out larger than the original (rare, but possible for already-optimized files), the tool flags it and lets you keep the original instead.
This matters most for exactly the kind of PDF that's hardest to shrink well: a phone-scanned document or a report full of high-resolution photos, where file size balloons far beyond what the actual content needs for on-screen reading or email attachment limits. Since compression runs in a background Web Worker with a real progress bar, you can watch it work through a large file instead of staring at a frozen page, and everything happens on your own device regardless of file size.
How to Compress PDF
- Upload the PDF you want to shrink.
- Pick a preset (Minimal through Extreme) or switch to Target Size and type a goal like "1 MB."
- Compare the before/after preview and the percentage saved.
- Download the compressed file, or keep the original if compression didn't help.
Frequently asked questions
Is this a real compressor, or does it just re-save the file?
It's a real image-recompression pipeline, it decodes, downsamples, and re-encodes every embedded image, which is why it can achieve genuine 50%+ reductions on image-heavy PDFs, not the 2-3% you get from just re-saving.
Can I compress a PDF to an exact size, like 500KB?
Yes. Switch to Target Size mode, type your goal, and the tool searches across quality/resolution settings to get as close as possible, and tells you honestly if that exact size isn't achievable.
Does compressing reduce text quality or make it blurry?
No. Text and vector content are left alone; only embedded raster images are downsampled and re-encoded, so document text stays sharp.
Is my PDF uploaded to compress it?
No, the entire pipeline, decoding, resizing, re-encoding, rebuilding the PDF, runs in your browser using a Web Worker, so your file never leaves your device.
Does it work on mobile for large scanned PDFs?
Yes, it runs in a background Web Worker with a real progress bar, though very large scanned PDFs will naturally take longer on a phone than a laptop.
Related tools
- OCR Scanned PDF: Make scanned PDFs searchable and selectable with OCR.
- Merge PDF: Combine multiple PDFs into one document, in any order.
- PDF to JPG: Export every page of a PDF as a JPG or PNG image.
- Add Watermark: Stamp a text or image watermark across every page.