ANy solid-state H-bridge should be able to handle PWM. THe way PWM works has more to do with the way a motor's inductance and inertia more than it does with the H-bridge. THe H-bridge just has to be fast enough.
In Ikalogic's schematic they've combined the inputs with the enables. That's kind of stupid, but does make it very simple to use. What you need to do is separate them, so you can turn your motor on and off with the inputs and send PWM to the enables to control speed.
EDIT: I may be mistaken. If so, you would still have to separate the inputs and enables, but you would set the enable high and send PWM to the input pin instead.
I'm not sure which way is correct, but it won't hurt anything to try both ways. Use whichever one works.