A 100 KB ceiling is stricter than the 200 KB limit many forms publish. This page selects that tighter target on the same compressor as compress PDF. Pages are redrawn as JPEG images in the browser, from a clearer setting toward a blurrier one, and the first file at or under 100 × 1024 bytes is kept. If none of the steps fit, the note says the target was missed and offers the smallest file the list produced. That sentence is the result, not a failure of the download button.
Expect to miss the target when the PDF is a colour scan of a full page, a slide with photographs, or more than a couple of pages. A single grayscale page with wide margins sometimes fits. The picture will look softer than the original, because that is how a small JPEG is small. If you cannot read a name or a date in the download, do not submit it. Go back to the original, crop blank margins in a photo tool, or use 200 KB when the form allows it.
Nothing is uploaded, and nothing is stored. Text in the output is a picture, same as on the main compress page. Twenty-five pages is the maximum, though a 25-page file has almost no chance of a readable 100 KB result. Join files first with merge PDF only when the limit applies to one attachment. Turn loose photos into a PDF with JPG to PDF before you compress them. Reduce PDF size leaves the target unset if you want any saving rather than a number.
Keep the file you started with. A miss at 100 KB is useful information: this document, treated as pictures, does not fit that ceiling at a resolution this page still considers a document. The tool stops at its lowest planned quality instead of inventing a smaller, blank file.