Few things are more annoying than opening a scanned document and finding the pages sideways or upside down. Rotating a PDF fixes the orientation so the file reads and prints correctly — and unlike rotating in a viewer, a proper rotation is saved into the document itself.
Most rotation problems come from scanning. A page fed into an automatic document feeder in the wrong direction, or a photo taken with a phone held sideways, produces a page that is turned 90 or 180 degrees. Some viewers let you rotate the view temporarily, but that change is lost as soon as you close the file.
Rotating the view in a reader like a browser or Acrobat only changes how you see the page in that session. To fix the file for everyone — so it prints the right way and looks correct in any viewer — you need to write the rotation into the PDF. That is what the Rotate PDF tool does.
You rarely need to rotate an entire document. Because ColaPDF shows every page as a thumbnail, you can rotate just the two or three pages that came out wrong and leave the rest untouched.
Yes. The rotation runs entirely in your browser, so your document is never uploaded to any server.