How does it know which page is the last one?

It counts the pages in your file and removes the one at the end, whatever number that is.

What if my document has only one page?

The tool says so instead of handing back an empty file.

No. The browser reads the file and writes the new one locally.

Drop the final page of a document, whatever number it happens to be.

Drag & drop a PDF, or choose it from your device. It stays on your machine.

Choose file

Which page