I fixed the problem. The Scan page in HP Smart has an icon for "Auto-enhancements". I clicked on this and found an option "Orientation Rotate Images right side up". It was on by default. I turned it off, and now pages print correctly. Why an option to rotate images rightside up instead rotates them upside down, only HP knows. My pages were all landscape, all facing the same way.
By the way, I don't see anything about "Book" or "Tablet" anywhere in the application, so I have no clue what Shlomil is referring to.
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