I don't think I'd be comfortable with it having elaborate editing functionality. PDF editing in a browser is finicky, and an enormous bug fest.

I do PDF editing offline, on the desktop, then re-upload to paperless. Not the most integrated flow, but much more bulletproof. I want the PDFs themselves to be immutable once on paperless. Only metadata should be editable.

It keeps an “original” PDF and presents a working copy for modifications like OCR and metadata. Rotation is important for OCR, so rotate-and-redo is a worthwhile feature.

There is an issue about this, basically it's not going to happen because it is editing functionality. They suggest using another solution before import (build a pipeline).

It does have rotate clockwise/anticlockwise

Where? I'm pretty sure my instance doesn't.

In Settings I have "Use PDF viewer provided by the browser" checked and then see the screenshot:

https://imgur.com/TIOv1kK

The renderer does maybe. But it isn't saved and not used for OCR.

So paperless doesn't have rotating functionality.

you can use an opensource tool for scanning, like NAPS2, which will let you rotate before you mail it to paperless-ngx