But I’m wondering if the publisher (whoever created the PDF) did it in such a way that permissions on the file allow someone to OCR, e.g. “change” it.
When creating PDFs, there are a number of permission options that can be placed on the created file to allow for example, opening, reading, printing, editing, … That’s in the ANSI spec for PDF and implemented in PDF creating software.
Try: “print” a new PDF from the book with macOS Preview app (if the publisher allows the file to be printed) then OCR the new one.