By default, when using the ruler tool or gridlines to check alignment, scale will default to 1 : 1. You can change the scale (and also units of measure) in the dimensions pill on the proofing screen.
To change the scale
Step 1
Click the dimension pill, and set a new scale. For example from 1 : 1 to 1 : 2.
To learn how to use the ruler tool, view this article.