Why your PDF is heavy, and what can actually be done
A PDF is rarely heavy because of its text: a thousand pages of pure text fit in a few hundred kilobytes. What weighs is the images — a scan, a photo, a full-page screenshot.
Inside a browser there is exactly one way to act on that: redraw every page as an image and recompress that image. It is devastatingly effective on a scanned document, where dividing the size by five or ten is routine. And it is a bad idea on a text PDF.
What other compressors do not tell you
Compressing a PDF that contains real text turns it into a series of pictures. The text becomes pixels: no longer selectable, copyable or searchable. A contract, a CV, a thesis loses the thing that made it useful — and the file can even end up larger, because a page of text compressed as JPEG weighs more than the text ever did.
So this tool analyses your document before touching anything and tells you which of the two cases you are holding. If the result comes out bigger than the original, it says that too and tells you to keep the original. No competing service shows either.
Frequently asked questions
Will the text in my PDF stay selectable?
No. Compression turns the pages into images. That is why the tool warns you when your document contains text: on that kind of file, backing out is often the right call.
How much can I expect to save?
On a scanned PDF, commonly 70 to 90 %. On an already-optimised text PDF, sometimes nothing — and it may grow. The tool shows you the resulting size before you download.
Is my document sent anywhere?
No, and for a PDF that is the point that matters most. Everything happens in your browser: open the network tab, nothing leaves.
Which settings should I pick?
For a scan meant to be read on screen, medium quality and screen rendering are enough. For something to be printed, raise the detail to 300 dpi and the quality to high.