Three jobs that are really one job
Rotating a page, deleting a page and reordering pages all come down to the same operation: build a new document that references the pages you want, in the order you want, with the orientation you want. That is why they are on one screen here instead of three, most documents that need one need another.
The important consequence is that nothing is re-rendered. Each page is copied as a complete object: same fonts, same vector text, same image data. A rotated page is the identical page with one property changed. This is not true of tools that flatten pages to images first, which is why those leave text looking soft.
Rotation that actually sticks
A sideways scan is usually not a sideways image, it is a correctly-oriented image with an orientation flag some viewers honour and others ignore. Rotating in your PDF reader often changes only the view, and the file arrives sideways at the other end anyway.
The rotation applied here is written into the page's own rotation property and is cumulative with whatever the page already carried, so it survives the download and shows correctly everywhere, including in the automated checks an upload portal runs.
The duplex-scan problem
Scanning a double-sided document on a single-sided feeder produces a predictable mess: all the fronts, then all the backs, often upside down. The fix is exactly the three operations on this page, rotate the reversed side by 180°, delete the blanks, and interleave the order.
Deleting blank pages is worth doing for its own sake before an upload: fewer pages means a smaller file, and unlike compression it costs nothing in quality. If size is the goal, try this before the compressor, removing pages is lossless, compressing is not.
Before you send it on
Once the pages are right, two things are worth a moment. If the document is going to someone outside your organisation, check what it is carrying with the metadata viewer, author names and software fingerprints travel with a PDF by default. And if only some pages are needed by the recipient, the split tool shares less than sending the whole file.