pdfpix

Compress PDF to 400 KB

or drop one here
Compression level
Target size
Choose a PDF file first.

400 KB is 409,600 bytes. It holds 25 text pages, 10 pages with pictures, 13 scanned pages, 20 phone photos of pages or 14 pages scanned in colour. A file that starts at 450 KB needs only a small cut, and the methods that change no pixel often find it.

How to compress a PDF to 400 KB

  1. Choose the PDF

    Press Choose a PDF, or drop the file on the page. The file is read in this tab and is not sent anywhere.

  2. The target is already set

    This page opens at 400 KB, so there is nothing to type. Pick a different level, or enter your own smaller number in KB, if you want another size.

  3. Press Compress

    Four methods race: copy the pages into a fresh file, re-encode the placed images, cut each embedded font down to the glyphs the pages draw, and, only when no other method reached the target, redraw the pages as images with the text kept on top.

  4. Read the check, then download

    Every candidate is opened again and its characters are counted against the source. The page shows the size, the method that won and the characters kept before it offers the download.

The four methods are described in full, with the measurements behind them, in how it works.

What fits in 400 KB

On the public files above 400 KB, the default methods cut the median file by 80%. A file that starts at 450 KB needs an 11% cut, which the structural rebuild or font subsetting often finds without touching a pixel.

DocumentPages at the default settingPages at the smallest setting
Text documentsPages at the default setting25Pages at the smallest setting25
Text with picturesPages at the default setting10Pages at the smallest setting10
Scanned pagesPages at the default setting13Pages at the smallest setting13
Phone photosPages at the default setting5Pages at the smallest setting20
Colour scansPages at the default setting4Pages at the smallest setting14

A 3 page colour scan of a US federal record went from 1.7 MB to 355 KB by re-encoding the placed pictures at 150 dpi.

The multi page scan

A scanned page came down to about 29 KB in the public run, so 400 KB holds a 13 page scan. The default methods stop at 150 dpi and quality 60, and keep a black and white page as a 1-bit image at 150 dpi, so the print stays sharp.

A page scanned in colour came down to about 27 KB at the smallest setting, so 400 KB holds 14 of them. If the paper is still on your desk, scan it again in greyscale. A colour scan of a black and white page stores three colour channels where one would do.

Neighbouring targets

300 KB is the step down and 500 KB the step up. Aim a little under the cap you were given: a file at 390 KB clears both the 1,024 and the 1,000 reading.

Questions

What is 400 KB in bytes?
409,600 bytes at 1,024 bytes to the kilobyte. A form that counts in thousands stops at 400,000, 9,600 bytes tighter. Aim at 390 KB when a form has refused you once.
Does a pdf compress to 400kb keep my text selectable?
Yes. Every candidate is read back and must keep 98% of the source's non-space characters. Across the public run, every output kept at least 99.99% of its characters.
Should I compress to 400 KB or split the file instead?
Split it if the form accepts more than one upload. A four page part at 400 KB keeps far more detail than a twelve page file at the same cap, because each page gets three times the budget.
How does a 450 KB file get under 400 KB?
Usually by font subsetting or the structural rebuild, which find the 11% without changing a pixel. If the file has pictures, the picture re-encode at 150 dpi is the next step.

Related tools

Each runs in a browser tab like this one, reads its own output back before the download, and needs no account. The footer links every tool.

Where to go next