As for all this talk about "drivers", I kind of feel like there's a little bit of confusion about what role a driver plays on "oldschool" printers verses modern ones.
The printers most widely used on personal computers from the dawn of the breed in the 1970's up through around the mid-1990's were descended from receive-only teletype machines. IE, they were a box that took ASCII input and typed it onto paper. In addition to knowing how to translate printable characters into marks on the paper they'd also generally understand at least a handful of additional "action codes"; besides the obvious ones (carriage return and linefeed) they'd usually know how to backspace, form-feed to a new piece of paper, at least sometimes they'd be able to do something useful with horizontal tabs... and that was about all that was "generically" defined.
If you were happy with your printer being limited to about the same level of special effects that you could achieve by using the keys on a standard Selectric typewriter then you didn't need a driver, you just threw text at the printer and life was good.
Obviously people started wanting more from printers; one pass underline, italics, boldface, proportional spacing,
additional fonts, and eventually, graphics
. Unfortunately there was no universal ASCII standards for these features, so printer manufacturers implemented special effects the same way terminal manufactures did; via Escape codes chosen completely at random.
Here's a list of Epson FX escape codes; compare them to the list of supported codes in the Apple Imagewriter manual and you'll find they're completely different.
Here's an abbreviated reference of basic HP PCL 4.x escape codes; also completely different. So... yeah. On one hand, all these printers are "compatible" without drivers
if you want them to print like a typewriter, but if you want
boldface italic unicorns to come out you need a driver specific to your printer.
If you're hooking up a printer to an OS that depends on graphics and unicorns you need a driver. But it seems like we're spending an awful lot of time worrying about drivers for a computer that has no unicorns, never did. YOU DON'T NEED A DRIVER FOR A PET. Unless you're writing your own software, and then you're writing the driver. The one exception to this I think might be significant is if you run into software that specifically wants a Commodore Printer; Commodore's printers for the PETs had their own special features that were pretty elaborate, like a data formatting mode and they could also print PETSCII graphics. If this is what you want then, well, you're not going to find a printer that does that. Your best bet is to start building your own adapter to capture the PET's IEEE-488 output so you can run it through your own translator that will emulate one of those Commodore printers and spit out a graphics file or whatever that you can print on a more generic printer.
Edit: Almost forgot: Post the mid-1990's (and there were some examples before this but they were rare enough you probably don't need to worry about them), after everyone's desktop computers became so infested with graphical unicorns that nobody thought they wanted plain text printers anymore, manufactures started building devices that could
only print pictures, they actually didn't bother with the least common denominator ASCII printer functions anymore. This is the one kind of printer that your PET is going to be completely hopeless talking to unless you have some newer computer sitting in between it and the printer to do translation. And like I said, I think your chances of finding a printer with an RS-232 serial port on it that falls into this category are pretty nil (unless you're going really out a limb into things like receipt or label printers... maybe?), you're probably *mostly* safe with Centronics printers, and obviously you have no converter to go straight from your PET to a USB printer so it doesn't matter that most USB-only printers *do* fall into this category to at least some extent.