The tool shows the size before and after, and how much was saved. If the file did not get smaller, no download button appears at all — a bigger "compressed" file is worse than the original, so the tool refuses to hand you one. That is not a failure of your file; it usually means the PDF was already compressed, or it is typed text rather than scans.
If you set a size limit and the file cannot reach it, the message says so plainly and tells you the smallest size it managed. It will not pretend the limit was met.
Three things help more than compressing harder. First, remove blank and duplicate scanned pages — an empty page still costs a full picture. Second, split the document and send it in two parts if the portal allows it. Third, if you scanned with a phone camera, rescan using your phone's own document scanner: it flattens the page and drops the background, which is far smaller than a plain photograph of paper.
Scanned documents are heavy because every page is a full photograph. A twenty-page scan can easily pass 30 MB, which most email systems reject. Compressing re-saves each page at a lower resolution, which usually cuts the size by half or more while keeping the text perfectly readable.
Important papers should not live only on your phone:
Als Amazon-Partner verdiene ich an qualifizierten Verkäufen.At normal settings, yes. At the strongest setting small print can blur.
Why did my file barely shrink?Text-only PDFs are already small. Compression mainly helps scanned pages.
Can I undo it?Your original file is untouched.