First, I don't recommend getting any e-reader if you main purpose is pdf. Use a tablet. (Or maybe the Remarkable.)
But, I just opened the included user manual (pdf) and it was fine doing high lights. Pretty much the same as with epub. (I was actually a bit suprised that it worked as well as it did. Maybe this is a very simple pdf, or I'm being a bit prejudice towards pdfs....
)
It's not as precise as I would like, if you want to change a highlight, it can be a bit of a burdon, but it works.
For me, it works just a tiny bit better than on my Kobo.