Compress PDF to 400 KB
Room for a scan of several pages or a short report with photos. The size box is set to 400 KB already.
- Free to use
- Works on any device
- Deleted after processing
- Text stays vector-sharp
- Sized for email
- Every page kept
- The original is untouched
Make your PDF 400 KB or smaller
Text stays sharp at every level · your upload is deleted as soon as the smaller file is built
Drag & drop file here
or choose a file from your device
How it works
Compress PDF to 400 KB in three steps
Add your PDF
A scan, a report, or several certificates already merged into one PDF.
400 KB is already typed in
The "To a size" option is already on, with 400 in the size box. Change the number if your form gives another limit.
Compare, then download
The old and new sizes sit side by side. Open the result and check the smallest print before you upload it.
400 KB on our test files
Seven files made for this test: typed reports with photos and scans of one to ten pages, each compressed on this setting. Measured on October 31, 2026.
| Test file | Before | After | Page DPI after | How it looks |
|---|---|---|---|---|
| Typed letter, 2 pages | 3 KB | 3 KB | No pictures | Unchanged |
| Report, 4 pages with 3 photos | 842 KB | 343 KB | 150 | Close to the original |
| Report, 8 pages with 6 photos | 1.86 MB | 280 KB | 110 | Photos good on screen |
| Scanned letter, 1 page, color | 1.33 MB | 123 KB | 150 | Close to the original |
| Scanned letter, 2 pages, color | 2.66 MB | 244 KB | 150 | Close to the original |
| Scanned report, 3 pages, grayscale | 4.94 MB | 257 KB | 110 | Sharp; small print fine |
| Scanned report, 10 pages, grayscale | 14.8 MB | 237 KB | 72 | Readable; small print soft |
Every file kept all its pages and its page size. Only the pictures inside were made smaller; the typed text in the reports stayed as sharp as before.
The tool steps down from 150 DPI to 110, 72, 50 and 36 and keeps the first step that fits, which is why several results sit well under 400 KB.
Where a 400 KB limit comes from
Limits of a few hundred KB usually belong to online applications where each document has its own upload box: a certificate, a mark sheet, an ID or a proof of address. 400 KB is roomier than the 100 or 200 KB set for a photo or a single certificate, so it tends to be the box for the longest document. Read the limit off your own form and type it in if it is different.
Read next: Compress PDF to 300 KB · Compress PDF to 500 KB · Merge PDF
Frequently asked questions about Compress PDF to 400 KB
How many scanned pages fit in 400 KB?
More than most people expect. In our tests two color pages kept the full 150 DPI at 244 KB, three grayscale pages fitted at 110 DPI, and a ten page grayscale scan came to 237 KB at 72 DPI, still easy to read on screen. With many more pages than that, the pages drop to 50 DPI, so check the result before you upload.
My one page scan came back at 123 KB. Why not closer to 400 KB?
When a file has to shrink, the tool starts at 150 DPI, sharp enough to read and print a page, and stops there if the file fits. It never adds weight to fill the limit, and a smaller file uploads faster. Our one page color scan made 123 KB at that setting.
Should I upload one 400 KB file or several smaller ones?
If the form has one upload box for everything, merge the pages with Merge PDF first and compress the result here. If it has a box for each document, compress each one on its own: a document that does not share the limit keeps more detail.
Will a report with photos still look good?
Yes, at this size. Our eight page report with six photos went from 1.86 MB to 280 KB with the photos at 110 DPI, which looks clean on a screen. The typed text stayed sharp, because real text is not a picture.
What if my PDF is already under 400 KB?
You get it back as it is. A typed two page letter of 3 KB was not touched in our test.
Full step-by-step guide
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