A scan usually arrives with more page around it than page. Cropping it makes it readable on a phone and smaller to send.
Crop a PDF →Free every day without an account on some tools. Your file is deleted the moment the job finishes.
The same box is applied to every page, or to the pages you name. It sets the crop box rather than cutting the content, which means it is reversible — and it also means what is outside the box is hidden rather than deleted. If something has to be gone for good, that is redaction, not cropping, and the page says so.
Yes, with the same margins, or page by page if they differ.
Removed. The page box is rewritten, so what you cropped away is not sitting outside the visible area waiting to be found.
Rotate it first, then crop.