How do I get a PDF under 200 KB?

Count the pages first. Under three, compress and you will almost certainly be there. Three to eight, convert to grayscale before compressing. More than about ten scanned pages, extract only the pages the form actually asks for — 20 KB per page is the floor where scanned text stays readable.

Can I set an exact target size, like 100 KB?

No compressor can promise an exact output size, because the result depends entirely on what is inside the file. What you control is the compression level; the size is the outcome. In practice you compress, check the number, and if it is still over you take a page out or drop to grayscale.

Does compressing twice make it half the size?

No. The second pass re-encodes already-encoded images, so it costs quality and returns very little size. If one pass has not got you there, change something structural — grayscale, cropping, page count — rather than repeating the same step.

The portal says my file is too big but my computer says it is fine.

Check whether the limit is in KB or MB, and check whether the portal counts all attachments together. Some also reject files above a page-dimension limit rather than a byte limit, in which case a document scanned at A3 will fail even at a small file size.

how to reduce pdf size to 200 kb

How to Get a PDF Under an Exact Size

"Make it smaller" and "get it under 200 KB" are not the same problem. The second one has a budget, and the budget divides by the number of pages.

Start with the arithmetic, not the tool

Divide the limit by your page count. That is your per-page budget, and it tells you immediately whether this is easy, awkward or impossible.

A two-page scan under 200 KB means 100 KB a page — comfortable, and it will still look clean. Ten pages under the same 200 KB means 20 KB a page, which is achievable in grayscale but will look soft. Forty pages under 200 KB means 5 KB a page, and no amount of clever compression gets a readable scan there. If you land in that last case, the answer is not a better compressor; it is fewer pages or a different file.

The same arithmetic explains a result people find baffling: compressing a text-only PDF that is already 90 KB and getting 88 KB back. There was never any image weight to remove. The file was already almost entirely instructions.

Over 80 KB a page: Easy. One compression pass, quality barely changes.
30–80 KB a page: Fine. Convert to grayscale first if it is a scan, then compress.
10–30 KB a page: Tight. Grayscale is essentially required, and text will look softer.
Under 10 KB a page: Not realistically reachable for scans. Split the document or resubmit fewer pages.

The order that actually works

Most people go straight to a compressor, get a number that is still over, and try the same compressor again harder. Running compression twice mostly costs quality without buying much size — the second pass is squeezing data that was already squeezed.

Work through the levers in order of how much they give you per unit of visible damage:

1. Crop the margins: A phone photo of a page usually includes desk, hand and shadow. Cropping to the paper can remove a quarter of the pixels before anything is re-encoded.
2. Convert to grayscale: A scan of black text on white paper has no colour worth keeping. Typically 20–40% off, and on a text document you will struggle to see the difference.
3. Compress: This is where the big number comes from on any image-heavy file — commonly 50–90% on a default-settings scan.
4. Drop pages: If the form wants a degree certificate and you scanned the whole booklet, extract the page they asked for. Nothing else is close to this efficient.

Why government and exam portals set these limits

The numbers are not arbitrary and they are not negotiable — they come from the storage the portal was budgeted for, often years ago, multiplied by the number of applicants. A limit of 200 KB across two million applications is 400 GB. That is why the box rejects your file rather than accepting it and resizing it for you.

It is also why the limits cluster where they do: 20 KB and 50 KB for a signature or a photograph, 200 KB to 500 KB for a certificate, 1 MB to 2 MB for a full document. If you are being asked for a signature under 20 KB, you are being asked for a small black-and-white image, not a document — resize it before compressing and it will fit with room to spare.

When the file will not shrink

Three cases account for nearly all of them. The file is already text-only, so there is nothing image-shaped to remove. The images inside were already compressed hard by whatever produced the file, so a second pass has nothing left to take. Or the page count simply exceeds the budget, which is arithmetic rather than a compression problem.

Two things that never help, however often they are suggested: zipping the PDF, which saves a percent or two because the streams inside are already compressed, and renaming or re-saving the file, which changes nothing at all.