How do I rotate a document in Adobe Acrobat DC "grade-wise," so not by 90 °?

There's no built-in option to do that. When you run Text Recognition on a file Acrobat does it automatically, but if the file already contains text then your only option (that I'm aware of) is to use a plugin or a script, like this one I've developed: Custom-made Adobe Scripts: Acrobat -- Deskew PDF Pages