Drop a PDF that displays sideways or upside down, pick the turn, download it fixed. Every page turns together, and the turn adds to whatever rotation each page already carries, so a document scanned sideways comes out upright instead of merely turned a different wrong way.
Three turns cover everything. 90° right for the common scanner sideways, 90° left for the other one, 180° for upside down. The turn applies to every page; the mixed case (one landscape page in a portrait report) is a job for the extract tool, this one, and a merge: three stops.
Nothing is re-rendered. Rotation in a PDF is an instruction to the viewer, not a transformation of the content: text stays text, images keep their bytes, and the file size barely moves. The output is the same document, with each page carrying an instruction about which way up it should be drawn.
Where sideways PDFs come from. Scanners with sideways feeders, phone scans taken in landscape, exports from software with its own ideas about orientation. The fix takes seconds because only the orientation instruction changes.
Batches welcome. Ten sideways scans take one drop and one download each, with a ZIP at the end.
The turn is written into the file itself, so the page opens the right way up wherever it is next opened.