Rather infuriatingly, the "Title" field of PDFs I've downloaded from Paizo is exactly the same as the cryptic filename I was hoping to dispose of. In other cases, the title field doesn't appear (from other publishers), and I imagine that in some cases there's even a title in the title field.
Obviously this is something that would take a lot of work to fix, but if you ever find yourself short of improvements to make, I'd appreciate anything that could be done. It makes it hard to use my PDFs when I can't recognize them readily, and renaming them will be a long task if I decide to do it by hand.
The file name we assign PDFs is not entirely cryptic (it's the product code). Certainly it would make sense to fix the meta data in the file, however, a customer would not be able to edit this due to our security settings. I'll take a closer look and this and put it on my to do list.