PDF Size Reducer
Shrink a scanned PDF
Recompresses the pictures inside it. Everything else is left exactly as it was.
Nothing is uploaded. Contracts and scans stay on your machine.
- 1PDF
- 2Quality
- 3Smaller PDF
The PDF
How hard to squeeze
- No upload
- Text left untouched
- Runs offline
- Only JPEG images
How it works, and what it cannot do
Most oversized PDFs are scans: a thin wrapper around a few very large JPEGs. This tool finds those JPEGs, decodes each one, redraws it on a canvas at the resolution you chose, re-encodes it at the quality you chose, and writes the result back.
The file is not rebuilt. The original bytes are kept and the replacements are added as an incremental update — the same mechanism a PDF reader uses when you annotate a document. Your text, fonts, bookmarks, form fields and signatures pages are left exactly as they were, and if a replacement would come out bigger than the original image it is skipped.
What it cannot do. It only recompresses JPEG (DCTDecode) images. A PDF whose bulk is text, fonts or vector artwork will barely change, and the tool says so instead of handing you a file that is the same size. Images stored as PNG-style FlateDecode, JPEG 2000 or CCITT fax are left alone. Encrypted PDFs are refused rather than corrupted. If a file uses a cross-reference stream and your reader rejects the result, keep the original — it is untouched on your disk.
Questions people actually ask
Most tools that shrink a PDF ask you to upload it to their servers first. If the document is a signed contract, a passport scan or a client's accounts, that is a decision you may not want to make. This one never sends the file anywhere.
Is this PDF size reducer really free?
Yes. There is no account, no email address, no watermark, no page limit and no paid tier hiding the useful settings. It is one of nine free instruments KaiOrb publishes.
Does my PDF get uploaded to a server?
No. The file is read and rewritten by your own browser. You can disconnect from the internet after the page loads and it still works, which is the simplest proof that nothing is being sent.
How much smaller will my PDF get?
It depends entirely on what is inside. A scanned document is mostly JPEG images and commonly halves — a one-page scan in our testing went from 84 KB to 39 KB. A PDF that is mostly text and fonts will barely change, and the tool tells you that rather than handing back a file the same size.
Will it ruin the quality?
You choose. Four quality settings run from barely-visible change to maximum compression, and a separate resolution control. Text drawn as text is never touched — only the pictures are recompressed.
Why did it refuse my file?
Three cases are refused on purpose rather than producing a broken document: encrypted PDFs, PDFs with no recompressible images, and PDFs that store their objects in a compressed structure this tool will not rewrite. Your original is never modified.
Does it work on a phone?
Yes, in any modern mobile browser. Very large scans may exhaust memory on an older phone, and if that happens the page says so instead of hanging.
Part of nine free KaiOrb instruments — all in-browser, none of them upload your files.