Every page is shown as a preview with its own rotate-left and rotate-right buttons, so a scan that is wrong on only some pages, or an affidavit with one landscape annexure, can be fixed page by page. The buttons at the top turn all pages together when the whole document is sideways.
Rotation in a PDF is a single number on each page, so this rewrites that and copies everything else through untouched. The text stays text, the file stays the same size, and nothing is re-encoded.