Be realistic about 200 KB
This target only works for very short documents. A single scanned page can reach 200 KB and remain legible. Two or three pages will fit but look rough. Anything longer than about five scanned pages cannot reach 200 KB in a state you would want an official to read.
If your document is text rather than scans, 200 KB is comfortable even for a long file — a hundred pages of plain text is smaller than one photograph.
Why so many forms ask for exactly this
Limits of 200 KB, and the related 100 KB and 300 KB, are common on government and examination portals — particularly for document uploads attached to applications, where the form was designed around storage constraints that have not been revisited in years. The limit is usually per file, so splitting a multi-page document into separate uploads is often allowed and always worth checking before you compress a document into illegibility.
Scanning settings matter more than compression
At this size the single most effective thing is not the compressor — it is how the original was made. A page scanned in greyscale at 200 dpi will land near 200 KB on its own. The same page scanned in colour at 600 dpi can be twenty times larger, and compressing it down to 200 KB throws away everything that made the high-resolution scan worth having. If you still have the original document, rescanning is usually better than compressing.
If the tool says it cannot reach the target
That message is accurate rather than a failure to try. The tool reduces image quality until it runs out of room, then reduces the resolution and searches again. When it still cannot fit, the document has more pages than 200 KB can hold. Split the file, or try 500 KB and check whether the stricter limit was real.