The problem involved something I'd made in Postscript, which was then converted to PDF (with ps2pdf), because of something that ought to have been my first clue about the widespread insanity on this planet. Why PDF is widely regarded as superior to Postscript has never made a lick of sense, since it adds nothing but subtracts a good deal. Until today, however, I had regarded it as a nearly harmless form of compressed-Postscript. After all, there are simple tools to convert Postscript into PDF, so one can work in a human-readable language and yet deliver in PDF to those who prefer it. But that was before I encountered the "Auto-Rotate" brainwave. My simple problem was needing to turn even-numbered pages upside-down because the print-shop with the best price could only do long-axis duplexing. That's very easily done. The problem is that ps2pdf in its wisdom ignores that sort of thing, thinking it will do us the favour of making everything be right-side-up even when we clearly instruct it otherwise.
The solution incidentally is to pass "-dAutoRotatePages=/None" to ps2pdf.
That got me wondering: in Postscript, a language where one can be perfectly precise about exactly what orientation each element is to have, of what possible use is an auto-rotate feature? How could any sane person think such a feature a good idea? The answer is that no sane person could.
The Ghostscript people say very little about this dubious feature, except that they implemented it in order to be compatible with Adobe's Acrobat-Distiller. (In Acrobat-Distiller the solution is to uncheck the "Auto-Rotate Pages" option.) But is that an acceptable excuse? I think not. After all if Acrobat-Distiller contains a blatant bug does one faithfully emulate the bug in order to be compatible? Similarly if Adobe implements the dumbest idea this world has ever seen, does one follow them into the abyss?
Adobe, by the way, is responsible first for giving us Postscript which is a good thing, then for Portable-Document-Format (PDF) which sounds like a good thing but isn't. Why Adobe wants the world to get hooked on PDF is obvious: that way they get to sell a lot of overpriced software. But why are the majority of us humans so gullible that we go along with a scheme that enriches Adobe while making the rest of us suffer? Back when IBM regretted having made the PC-architecture so open that everyone was making PC's and yet IBM was making no money from having created it, they gave us the PS2 in an effort to "correct" their blunder. That effort failed and we kept right on using PC's made by everyone except IBM. So we humans do sometimes behave like sentient beings...
[A few words of explanation for the reader unfamiliar with the relationship between Postscript and Portable-Document-Format (PDF): PDF is a variant of Postscript; it is a subset of Postscript, and the format includes compression. The conversion (from Postscript) involves executing the program and saving only the output-producing statements; for more info, google for Postscript and Distiller. One important point is that Postscript is a general-purpose programming-language, PDF is not. And, whereas Postscript has always been "open", until 2008 the PDF was proprietary. Incidentally, both Postscript and PDF are inherently vector-graphic formats, but both also support raster-graphic images.]
It was Adobe who created this "feature" of negative value. It was Adobe who chose the wrong default for this option that no sane person wants. However it was Ghostscript who turned it into something truly evil. The different user-interface turns an act of stupidity into a sin of the highest magnitude, since it makes the turning-off so incredibly hard to find.