text is awkward how it's almost up against the edges but not quite. Either stretch it all the way out so it looks like it's connected the outside of the sig or make it smaller with more breathing rooom.
You can create a text box by clicking and dragging it and it will have anchor points. stretch it out to the size of the canvas and center the text within it from the paragraph tab. You can also use rulers to make sure you get the vertical alignment right.