Compress PDF to 100KB

1. 1

   Add the PDF

   Drop the scan or document onto the page. The size breakdown shows straight away whether the bytes are in pictures, fonts or page content — which decides what can reach 100 KB.

2. 2

   Keep Strong

   The page opens in Strong: pictures at 96 DPI, text untouched. On scans it is usually the smallest mode as well — the estimate under the mode picker shows every mode's size for your file before you run it.

3. 3

   Compress and read the size line

   The result says in plain words whether it is under 100 KB. On Pro, the 100 KB target is already filled in and the tool searches for the gentlest settings that fit.

4. 4

   Check the pages and download

   Look at the before-and-after page previews and the quality score, then download the file and upload it.

A PDF's size depends on what is inside it, not on how many pages it has. A letter exported from a word processor is text and fonts, and it is often under 100 KB already. A scan is different: every page is a photograph. An A4 page scanned in colour at 300 DPI is about 2480 × 3508 pixels — nearly 9 megapixels — and even a well-compressed picture of that size runs to several hundred kilobytes. To get a scanned page under 100 KB, the picture inside has to get smaller in pixels and more compressed, and that is exactly what the modes on this page do.

What decides whether 100 KB is reachable

• Pages: each scanned page needs its share of the budget, so one page fits far more comfortably than four.
• Colour: a colour scan of a black-and-white document spends bytes on colour nobody needs.
• Resolution: 96 DPI is readable on screen for ordinary text; a 300 DPI picture is many times larger for no benefit on a portal.
• What is already in the file: the size breakdown shows how much is pictures, fonts and page content before you choose, so you know which lever will move the number.

The page opens in Strong because it is the strongest mode that leaves your text, links and form fields exactly as they were. That is usually enough for a one- or two-page scan. When it is not, these are the levers — and the estimate under the mode picker shows what each would do to your file before you press anything.

The levers, in the order to try them

• Strong: recompresses the pictures at 96 DPI. Text stays selectable and sharp, because it is not a picture.
• Flatten: turns each page into a single picture at 96 DPI. It only helps when a page holds things Strong cannot shrink, such as vector drawings; on a scanned page it usually comes out larger than Strong, so check its estimate first.
• Grayscale (Pro): for documents that are black and white on paper; it drops the colour data the scanner added.
• Automatic target (Pro): the target field is already set to 100 KB, and the tool searches for the gentlest settings that fit instead of making you try modes.

Upload forms usually count a kilobyte as 1,024 bytes, so 100 KB is 102,400 bytes; a few count 1,000. The size line on the result uses 1,024-byte kilobytes too. If your form rejects a file that reads as 98 or 99 KB here, it is counting in thousands — aim for about 97 KB.

Before you upload

• Check the notice: limits differ between portals and between application rounds, and the number in your form's own instructions is the one that counts.
• Check the file type: portals that ask for 100 KB often want PDF for documents but JPG for photos and signatures — the image pages handle those.
• Check readability: open the downloaded file and zoom to 100%. If the reviewer cannot read it, being under 100 KB does not help.

Some documents cannot reach 100 KB without becoming unreadable — a ten-page colour scan, a photo-heavy brochure, a certificate scanned at high resolution on a patterned background. The result says so plainly rather than handing you a file you cannot use.

What to do instead

• Upload pages separately if the portal allows several files: split the PDF and compress each part.
• Remove pages that are not required, such as blank backs of single-sided documents or instruction sheets.
• Rescan at a lower setting — 150 DPI in grayscale is plenty for text — and compress that instead.
• Send an image instead if the portal accepts JPG for that document: a one-page scan as a 100 KB JPG is often just as readable.

• PDF compressor — all modes
• Compress PDF to 200KB
• Split a PDF
• Remove PDF pages
• Photos to PDF
• Resize image to 100KB
• Photo and signature resizer