Did you rotate the view in the page panel in InDesign? That means, only the view is rotated, not the document itself.
It is not much work to rotate it in Acrobat Pro. One command for the whole document.
I rotated each individual page using the inDesign page editor. If that is what you are referring to, then yes, I guess I only rotated the view. If there is a way to rotate the entire document in inDesign, which I have continued to search for but cannot find, that would help.
Will keep the Acrobat Pro option in mind for future, but as of now, I'm not sure I can justify $180/year for that convenience alone, for the annual, single calendar. Not the end of the world to rotate individual pages as I'm doing now, in the PDF viewer.