How do I anchor the annotation within the family so that when I change the page size it increases and decreases size from the center of the model?
Align Annotation within family
In the Ref Level (Plan) view in the family there should be two planes which define the family origin - these are usually called Centre Front/Back running right to left and Centre Left/Right running north to south.
These origin defining planes should be pinned.
The family origin is the intersection of these two planes
Make your text centre aligned and move it so that its centre is over the origin.
Move your symbol so that the "insertion point" of the symbol is directly over the origin.
Accepted solution
So, I couldn't snap the annotation to anything to anchor it and it turns out within the annotation family the reference planes weren't visible. I changed this and added dimensions to fix this, and it worked like a charm.
