CompressaPDFto250KB

What 250 KB realistically means

250 KB turns up on voter ID, e-District and ESIC portals, and on plenty of bank and insurance forms. It is noticeably easier than 200 KB, and most address proofs, domicile certificates and affidavits reach it on medium quality without any visible change.

How to get there

• Medium quality first — for a one to three page certificate this usually clears 250 KB on its own.
• Greyscale if it is close. A colour scan of a black-and-white document is carrying three channels it does not need.
• Crop the scanner border before dropping quality. It costs nothing on the page and can be a surprising share of the file.

If you are uploading a photograph of a document rather than a scan, retaking it in daylight and filling the frame with the page will do more for the file size than any setting here.

If it still will not fit

There are three moves left, in order of how much they cost you:

• Greyscale. A colour scan of black text carries three channels describing grey paper — dropping them is often a third of the size, at no cost to legibility.
• Crop. A scanner's black border and wide margins are bytes spent describing nothing. Trim them, then compress.
• Split. If the limit is per file rather than per submission, send the document in two parts. This is almost always allowed and almost never tried.

What does not help is compressing twice. The second pass re-renders an already-rendered page: you lose quality and save almost nothing.

Why the file was so large to begin with

A PDF from a word processor is a few kilobytes a page, because it stores text as instructions. A scan stores a photograph — an A4 sheet at 300 DPI is roughly 8.7 million pixels — and a scanner that saves those without much compression produces several megabytes per page.

That is the whole story behind almost every oversized PDF. It is not corruption and nothing has gone wrong; it is eleven photographs in a wrapper.