The frustration this solves is specific: you rotate a PDF in your reader, it looks correct, you send it, and the recipient opens it sideways again. Most readers rotate the view without changing the file, and some will not even offer to save it. The rotation you applied was never in the document.
What this changes
PDF pages carry a rotation attribute that every reader is required to honour. This tool sets that attribute in the file itself, so the page is genuinely rotated as far as any software is concerned — your reader, the recipient's reader, the printer, and whatever system is going to process it.
The page content is not touched. Nothing is re-drawn, re-rendered or re-compressed; only the instruction about which way up to display it changes. Text stays selectable, and the file size barely moves.
Rotating only some pages
Leave the page selection empty and every page rotates. That suits a document scanned entirely the wrong way round. Fill it in — "2, 5-8" — when only some pages are wrong, which is the usual case with a mixed scan where landscape tables were fed sideways.
Rotation is added to whatever the page already has, not set absolutely. A page already rotated 90° that you rotate another 90° ends up at 180°, which is what you would expect from pressing the rotate button twice. It also means running the tool twice compounds rather than repeats.
- 90° clockwise — for a page lying on its left side.
- 90° anticlockwise — for a page lying on its right.
- 180° — for upside-down pages, common when a stack was fed into a scanner the wrong way.
- Only right angles are offered, because those are the only values the PDF specification allows.
Why arbitrary angles are not possible
A PDF page rotation must be 0, 90, 180 or 270 degrees — the format simply has no way to express anything else. Straightening a scan that came out at a slight angle is a different operation entirely: it means re-drawing the page content onto a new one, which turns text into an image and undoes everything that makes a PDF worth having.
Encrypted files are refused with an explanation rather than an obscure failure. Everything happens in this tab, and nothing is uploaded.
Rotate before you number or watermark
Anything stamped onto a page — page numbers, a watermark — is placed relative to the page as it stands at that moment. Rotate afterwards and the stamp rotates with the content, so a footer ends up running vertically up the side. Do the rotation first, then add anything on top.