What 300 KB is good for
A 300 KB limit sits between the tight sizes used for single certificates and the roomy ones used for reports. It suits documents that are a little heavier than plain text: an affidavit on stamp paper, an experience or relieving letter on a printed letterhead, a no-objection certificate with a coloured seal, or two or three scanned pages that have to arrive together.
Typed PDFs of this kind usually come in well under 300 KB through the lossless first step, so their text stays selectable and nothing about the pages changes. Scans are where the limit starts to matter.
Scans with seals, stamps and letterheads
Stamp paper, notary stamps and letterheads are printed in colour, and a reviewer may look for them. At 300 KB there is usually room to keep colour for a few pages, so leave black and white unticked and look at the preview first. If small print looks soft, try black and white: printed text becomes crisp, though the colour of a seal is lost. When the colour copy comes out soft, the tool makes a black and white copy as well, so you can compare the two before choosing.
- Scan the whole page, edge to edge, so a stamp near the border is not cut off.
- Keep pages in the order the form expects; the tool never reorders them.
- Remove blank backs of single-sided pages before scanning, or leave them out of the PDF.
Several pages in one upload
When a form allows one file for a set of pages, the 300 KB is shared between them. Every page is redrawn at the same sharpness level, so no single page ends up much worse than the rest. The result shows the DPI used: above roughly 100 DPI, normal printed text reads comfortably on screen.
Other sizes
If the form asks for less, compress PDF to 200 KB explains what to expect; if it allows more, compress PDF to 500 KB leaves room for colour on more pages. Any other number works on compress PDF.
Built on two open-source projects that run in your browser: qpdf, compiled to WebAssembly, for the lossless rewrite, and Mozilla's PDF.js to redraw pages when that is not enough.