Reduce the size of a PDF so it fits an email or an upload limit. Most of the weight in a large PDF is its images, and this recompresses them; you choose how hard to push before downloading.
The finished size is shown next to the original, so you can tell whether you have gained enough or need to push harder.
Compression happens in the browser. A confidential contract does not have to be handed to a stranger’s server to be made smaller.
Compress it here first — scanned documents and image-heavy files usually shrink a lot. If it is still too big, split it into parts and send them separately.
Images are recompressed, so at stronger settings they soften. Text and vector content are unaffected. Use the lightest setting that gets you under your limit.
A scan stores a photograph of every page, often at a much higher resolution than anyone will look at. Recompressing those pictures is usually where the whole saving comes from.