When a form rejects a PDF for size, work backwards: check the limit, find the heavy pages, then shrink in steps until it fits.
Upload forms are blunt: a file is under the limit or it isn't. When your PDF is over, the fix is a short loop — measure, reduce, check — and it starts with reading the form correctly.
Read the limit before you touch the file
Every form states its limit somewhere — commonly 1 MB, 5 MB, or 10 MB. Writing it down before you start prevents the usual mistake: compressing to something arbitrary, checking the wrong file, and submitting a copy that's still too big.
Find what's heavy
A scanned PDF is heavy because each page is a full-size image. That's the file's weight, and it's where compression earns its keep. A 40-page scan of 9 MB can usually drop under 5 MB with the text staying clear.
Reduce in steps, check between each
Compress at one level, download, and check the new size against the limit. If it still misses, decide whether to compress harder or cut pages. Trying to hit the limit in one maximal pass is how files end up unreadable — yet another rejected submission.
Cut pages before compressing harder
If the PDF mostly needs one section — the declaration, a single form page — extract just that range. A smaller document needs far less compression to fit, so the text you keep stays sharper. Removing pages and compressing are different fixes; use the cheap one first.