Split a PDF by file size

Almost every reason to split a PDF by size is somebody else’s limit. Mail servers reject attachments over twenty-five megabytes. Filing portals cap uploads at ten. A form insists on five and gives no reason. The document is what it is, and it has to arrive in pieces that each fit.

Measured, not estimated

A part is built and then weighed. If it is over the limit it is divided and the halves are weighed again, until every part actually fits. That matters because a PDF’s size is not the sum of its pages: fonts, images and structures are shared, so a ten-page slice of a hundred-page document is rarely a tenth of the file.

Estimating instead would be faster and would produce parts that are sometimes over the limit, which is the one thing this tool exists to prevent and which you would only discover when the upload was rejected.

The whole document is measured once first and an even division guessed from that, so a document whose pages weigh roughly the same settles on the first attempt rather than being taken apart page by page. Only the parts that turn out to be over get divided further.

When a part is still too big

A single page can be larger than the limit on its own: a full-page scan at high resolution, a detailed map, a photograph. Splitting cannot make it smaller, so it comes back as its own part and still exceeds the limit.

That is deliberate rather than a failure. Handing back the pages that do fit is more useful than refusing the whole job. If it happens, compressing the document first and splitting the result usually solves it, because the weight is in the images rather than in the structure.

Nothing is re-rendered

Each part is built by copying the original pages into a new document. Text stays selectable, images are not re-encoded, and no quality is lost. The parts are smaller because they contain fewer pages, not because anything in them was degraded.

Nothing leaves the device

The document is opened, measured, divided and packed by a worker inside your browser. There is no upload, no account, and no server copy, which matters when the reason you are splitting is that the file is too big to send to somebody you trust, let alone to a converter you do not.