Sideways PDFs usually happen when a scanner guesses page orientation incorrectly or a phone scan mixes portrait and landscape pages. The content is fine; the page rotation is just wrong.
The safest fix is to rotate the PDF pages instead of exporting the document through screenshots or print-to-PDF. A proper rotation updates the page orientation while keeping text, images, and file quality intact.
Use Rotate PDF for full-document rotation. If only a few pages are wrong, use the organize workspace where you can rotate individual pages before downloading.