In my project, I process a single product file by enabling various modes.
What I would like to do is to vary the name of the output PDF file in each
instance.

So, in processing a file, how does one go directly from prd_filename.tex to
myfilename.pdf rather than to prd_filename.pdf—assuming that it is possible?

Any tips or pointers to what I should be reading will be
greatly appreciated.

Alan