I thought I could work around this by using a virtual PDF printer, so I followed this hint to create one. The virtual PDF printer works in general, but apparently the detection of PDF protection was added in the pstopdf command line utility, which is utilized (I'm guessing) by all the methods I tried. So this method also failed, as evidenced by a note in the pdf.log file that's created.
I also have a Canon inkjet printer (a non-Postscript printer). I found that if I stopped the queue on the Canon and printed to it, then dragged the print job from the Canon's queue to the virtual PDF printer queue, the PDF would finally be produced as expected -- and without the Untitled.pdf filename to boot. I'm not sure what other types of printers this would work with; it may or may not have to be a non-Postscript printer.
[robg adds: I haven't tested this one, but I will soon, as I receive similarly password-protected PDFs from time to time, and it's a pain having to add each password to my Keychain. But I have to, as there's just no way I'll remember them, given that I open such PDFs only very occasionally. And for those who may complain that we've just posted a method of getting around PDF password protection, we really haven't -- you need to have the password in the first place to open and print the file.]

