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How to compress a PDF to under 100 KB

A 100 KB limit usually belongs to an application form that wants a single scanned page: the photo page of a passport, an ID card, a signed declaration. It is a tight limit for a scan, so it pays to know where the weight is and which order to try things in. This guide gives the target to type, the steps that work for one-page scans, and straight answers for files that will not fit.

Updated September 15, 20265 min read

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On this page
  1. 01Why 100 KB is harder than it sounds
  2. 02Compress a PDF to under 100 KB, step by step
  3. 03If the file still will not fit
  4. 04When compression is not the answer

Why 100 KB is harder than it sounds

A scanned page is one large image. Straight from a phone camera, or from a scanner set to colour at high resolution, that single image often weighs well over a megabyte, many times the limit. A PDF exported from a word processor is the opposite: a page of real text is usually far below 100 KB already.

So the job is almost always about one image per page, and every extra page makes it harder. Two scanned pages under 100 KB means each page gets roughly half the budget.

Compress a PDF to under 100 KB, step by step

Work on a copy that holds only what the form asks for, then compress.

  1. If the PDF has more pages than the form needs, keep only the required page with Extract Pages. Fewer pages leave more of the budget for each one.
  2. Open Compress PDF, add the file and type 0.09 in the target size box. The box is in megabytes, and 0.09 MB is about 94 KB.
  3. Run it. Compression lowers image quality first and scales images down only when quality alone cannot reach the target.
  4. Open the result and zoom to 100%. Check that names, numbers and the photo on an ID page are still clearly readable before you upload it.

Upload forms do not agree on what a kilobyte is: some count 1,000 bytes, others 1,024. Aiming for about 94 KB passes either way.

If the file still will not fit

Try these in order. Each one removes weight without making the page harder to read.

  • Grayscale PDF removes colour from the pages. For a black-and-white form or a printed letter that can cut the size noticeably with nothing of value lost. Keep colour for ID pages when the form asks for a colour copy.
  • Remove blank pages takes out empty backs of scanned sheets, which still carry the weight of a full image.
  • If the tool says the document would still be around a certain size even with every image removed, the images are not what is holding it back: the text, fonts and page structure alone are over the target. Keep only the pages the form needs and try again.
  • If the result reaches the target but the scan has become too soft to read, scan the page again at a lower resolution, such as 150 dpi in colour or 200 dpi in grayscale, or photograph it in even light. A cleaner source image stays legible at a smaller size.
  • If the form accepts more than one upload, send each page as its own file rather than forcing several pages into one.

When compression is not the answer

If the tool reports that the file is already under the target, there is nothing to do: upload it as it is.

If it reports that only a small share of the file is images, there is little left to recompress. A text PDF above 100 KB is usually carrying many pages or embedded fonts, and keeping only the pages the form needs is the reliable fix.

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Frequently asked questions

Real text stays sharp, because only images are recompressed. On a scan the text is part of the image, so check the result at 100% zoom before uploading.

The target box counts a megabyte as 1,048,576 bytes, so 0.09 MB is about 94,000 bytes. That is under 100 KB whether an upload form counts a kilobyte as 1,000 or 1,024 bytes.

No. The file is compressed without being transmitted and no copy is kept. You decide where the result goes.

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