Here is the page about feeding the antenna, which you probably found:http://www.k7mem.150m.com/Electronic_Notebook/antennas/yagi_vhf_feed.html
Although he says the folded dipole has a 300 ohm impedance, that specific antenna is
designed for 50 ohm feed IIRC, which means a folded dipole would be 200 ohms instead
of 50 ohms.
That makes life simple - see the drawing of the 4 : 1 balun using 75 ohm coax? You'd
do the same thing using 50 ohm coax.
Or you can just feed the driven element directly, and you should get a low SWR. But
for a clean pattern and predictable performance you really want to add a balun - if you are
going through the effort to build the antenna in the first place, you might as well finish
the job right. There are lots of kinds of baluns, and it can be as simple as slipping a
piece of braid over the end of the coax.
But that is one of the reasons I like the WA5VJB "Cheap Yagi" approach - it is simple to
build with wire and you can just solder the coax directly to the element (presuming you
use copper wire for the element, of course. Soldering doesn't work well with aluminum.)