How to rotate a PDF on iPad?

I am accessing PDF books on my iPad Pro and they will only display the Portrait style docs (ie: regular A4 e-book pages) on the landscape view of my iPad screen, which means I can only see about 1/3 of a page at a time. I’ve tried turning the iPad, however the documents do not turn with me. Ie: if I turn the iPad to portrait view, the document remains in landscape and the text is sideways.

How do I get a PDF to turn with the iPad so that I can flip between Portrait and Landscape view?

Am using software 12.3.1 if that’s relevant.