How do I compress PDF to 400KB?

Add the PDF above and press Compress; 400 KB is preset. The tool tries the highest image resolution first and steps down only until the whole file is below 400 KB.

Will an eight-page scan fit in 400 KB?

In our test, an eight-page colour A4 scan came to 360.2 KB at Recommended. Ten pages did not fit, even at Smallest, until the scan was saved in grayscale.

Why did my result end far below 400 KB?

Resolution goes down in fixed steps. When one step is still above 400 KB, the next can land well under it: our five-page scan went from over the cap at one step to 225.9 KB at the next.

Does 400 KB mean 400,000 bytes?

Yes. A kilobyte is counted as 1,000 bytes, so the result is at most 400,000 bytes. Sites that count 1,024 bytes per KB allow 409,600 bytes, so it passes there too.

Is it free, and does my PDF stay private?

One PDF at a time is free without an account, and the file never leaves your browser. Batches of up to 20 PDFs need a free account.

Compress PDF to 400KB Free — Long Scanned Files

How many scanned pages fit when you compress PDF to 400KB?

We tested colour A4 scans saved at about 710 KB per page. At Recommended, one page came down to 262.5 KB, three pages to 370.5 KB, five pages to 225.9 KB and eight pages to 360.2 KB, all under the cap. Ten pages (7.09 MB) stopped at 449.4 KB, over the limit.

The five-page file ended up smaller than the three-page one because only a lower resolution step brought it inside the cap; the tool steps down only as far as the whole file needs. Your own scans will vary with paper colour, scan resolution and how much of each page is photo, so read these numbers as a guide.

When a ten-page scan won't go under 400 KB

Recommended re-encodes the images already inside the PDF, so once it reaches its lowest step it cannot go further and suggests Smallest instead. Smallest redraws every page as a JPEG image: our ten-page colour scan reached 404.3 KB, still just over. Saved in grayscale first, the same ten pages came to 398.1 KB with Smallest and fitted.

Smallest leaves text unselectable, which rarely matters for a scan. If grayscale is not acceptable or still too big, remove blank reverse sides and any page the portal never requested, or split the document into two files when the portal has a second upload field.

400 KB, 300 KB or 500 KB: use the number on the form

Aiming lower to be safe only costs sharpness. Our three-page scan came out at 370.5 KB with a 400 KB target, the very same file as with 500 KB, while a 300 KB target pushed it down a resolution step to 245.5 KB. A one-page scan was 262.5 KB under all three targets, because it already fitted at the top step.

So type the figure your portal states. If it asks for 300 KB, use Compress PDF to 300KB; if it allows 500 KB, Compress PDF to 500KB keeps more detail. Some forms also give a minimum size; since compressing never enlarges a PDF, a file that already sits inside the range can go up unchanged.