Is it considered acceptable to ask potential PhD supervisors to recommend some of their recent publications for reading to get some idea what they are doing? Or is it considered the applicant's job to familiarize themselves with the supervisor's research? I could imagine that a busy professor might not want to spend much time writing about his/her research to a person who might not apply after all.
You could do that. However, do keep in mind that asking for something that you could very well do on your own isn't likely to win you any brownie points in their eyes.
A better option is to find and read several of his/her recent publications. Begin with a Google search, check out their webpage if they have one, search academic databases, etc. Don't email them for papers until you've found and read whatever is easily available. If you find one that is particularly interesting but you can't find the full text anywhere, then is the time to email asking if they'd be willing to share an author copy.
Familiarize yourself with what they have done. Know what aspects of the past research interests you most. THEN, you will be ready to ask what they are working on now, to have an idea whether you might fit in with their current/ongoing project(s). In this way, you are showing independence, initiative, and responsibilty, all good attributes for a PhD candidate to have.