It would seem you're not understanding the question. Let me reiterate. The OP wants to have two separate SBS based domains share resources:
"what i would like to do is be able to have them communicate with each other. have users on company A be able to use printers on company B's side of the network"
Connecting them across the network is not the issue here and is one that's quite simply resolved. If all you wanted was network connectivity between the two, you could make them one single shared subnet which is a whole lot easier than two separate subnets as it doesn't require routing between the two domains.
But, that's not the point.
In order to share resources, one must have trusts which as wanderer has pointed out, isn't possible with two SBS based domains.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.