How to compress a PDF
- Drop your PDF into the box above (or click to browse).
- Pick a compression level — Light, Balanced, or Maximum.
- Click Compress PDF and download the smaller file.
How it works
localdobe’s compression is built on trusted, battle-tested open-source PDF software — the same kind of professional PDF technology used by developers everywhere — running directly on your device instead of on a server. Instead of uploading your document for processing, that engine runs quietly in the background of your browser tab: no upload, no queue, no server round-trip. The first run downloads the compression engine once (a one-time download, cached after that); every run after that starts instantly, even offline. Curious exactly how a browser can do this? Read WebAssembly: how your browser became a PDF powerhouse.
The three lossless presets work by removing redundancy rather than recompressing images: duplicate fonts, unused objects, and repeated content streams are deduplicated and stripped out. The optional Shrink images preset adds what Ghostscript-style compressors do: it measures how large each image is actually drawn on the page, downsamples anything above 225 dpi to 150 dpi, and re-encodes photos as JPEG while keeping flat graphics lossless. Black-and-white scans, image masks and JPEG 2000 images are left alone. Want the full technical breakdown? Read how PDF compression actually works.
Compress to a specific size
Need your PDF under a particular limit — like an email or upload cap? Pick a target size and we’ll aim for it: 100 KB, 200 KB, 500 KB, 1 MB, 2 MB, or 5 MB.
Frequently asked questions
Can I compress a PDF without losing quality?
Yes. The Light, Balanced and Maximum presets only remove redundancy (duplicate fonts, unused objects, repeated streams) and never recompress your images, so pages look identical. If your file is mostly scans or photos, pick Shrink images: it resamples over-resolved images to 150 dpi and re-encodes them, which is lossy. Photo-heavy files and phone-camera scans often shrink by 50–90%; scanner or fax output that is already a 200–300 dpi JPEG shrinks much less.
Can I compress a PDF to a specific size?
Not to an exact byte count — results depend on the file’s contents. But Maximum gives you the smallest file, and PDFs with duplicated fonts, unused objects, or repeated content streams often drop by 20–70%, which is usually enough to get under an email or upload limit.
Can I compress a PDF for email?
Yes. Run compression to shed the biggest overhead first — for most email providers that accept up to 20–25 MB, that’s enough. If the file is still too big, splitting it and sending the relevant pages can help.
Why is the first compression slow?
Your browser downloads the compression engine once (a few MB compressed), then caches it. After that it starts instantly — even offline.
Is my PDF uploaded?
No. The engine runs inside a Web Worker in your browser. Your file never touches a server.