1. Open Rotate PDF
Choose the file. Each page shows as a thumbnail.
2. Turn one page or all
Rotate only the pages that are wrong, or every page at once.
3. Save
The rotation is written into the new PDF, so it stays turned in any viewer.
Questions
Is the rotation permanent?
Yes. It's saved in the file, not just on your screen.
Can I also reorder pages?
Use Organise PDF to rotate, reorder and delete pages in one place.
Related: Combine several PDFs into one file · Remove pages from a PDF