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Compress a PDF to 50 KB

Fifty kilobytes is a cruel limit for a scanned page, and some forms ask for it anyway. This page aims a little under the cap so the file clears it on either reading of "KB", then tells you plainly what it managed. One sharp page can get there; six pages of colour scan usually cannot.

PDF or PDF

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How to compress a PDF to 50 KB

  1. Tap Choose the PDF and pick the scan you have to get under 50 KB.
  2. The target is already 50 KB, so tap Compress to 50 KB.
  3. Read the size it reports — it will say whether it reached the cap or fell short.
  4. Save the file if you are happy with how the pages read.

Fifty kilobytes of scan, honestly

Fifty thousand bytes is about what one small photograph occupies. Spread across a single scanned page that is workable: black ink on white paper is the easiest thing in the world for an encoder to describe, so typed text survives. Spread across four pages it is twelve kilobytes each, and handwriting starts to dissolve.

The search walks down a ladder of quality and pixel size, and the last step weighs a real file rather than an estimate before handing it to you. If no colour setting fits, it will take the colour out — worth roughly a fifth on a photograph, not the third that the word greyscale suggests — and it tells you when it has done that.

What to try when it will not fit

Removing pages is the only reliable lever, because the fifty kilobytes are shared across all of them. After that, rescanning in black and white at 200 DPI instead of colour at 600 does more than any setting here: the compressor can only work with the pixels the scanner produced, and it cannot invent detail that a high-resolution scan wasted bytes on.

If the form will accept an image rather than a PDF, say so to yourself before you fight this number — a single photograph is a much easier thing to get under 50 KB than a document is, and there is a page here for exactly that job.

Questions

Why does it aim a bit under 50 KB rather than at it?
Because portals disagree about whether a kilobyte is 1,000 bytes or 1,024, and several reject a file sitting exactly on the boundary. Aiming ten per cent under clears both readings, and the true byte count is printed so you can check it against what the form displays.
It could not reach 50 KB. What did I get?
The smallest document it managed, with its real size named. Nothing is thrown away and there is no error message — you decide whether to use it, drop a page, or scan the original again.
Will the pages still be readable at this size?
For typed black-on-white text on one page, usually. For a colour photograph, an identity card or a page of pencil handwriting, fifty kilobytes is genuinely not much, and you should look at the result at full zoom before you upload it.
Does this work on a password-protected PDF?
No — a locked file cannot be opened here at all. The way round it is to open the document in a reader with the password, print it to PDF, and compress that copy instead.

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