I'm pretty sure that there's a non compete addendum in the agreement I signed when I was hired. What are the differences from that one?

This is just a general question about the whole union drive, since I am in very unfamiliar territory. If we vote for a union does that give the company the option of putting the raises in the new PEA on hold until a contract is negotiated? If so, does that mean we could be stuck at our current pay rate for quite some time....years even?