There are a few things options I typically change after installing a fresh new Inventor. I don't feel old enough to need to scale up my text and constraints but I like the look when they are larger. If you take a look at the following image this is the typical size of both text and constraints.
There are two separate options to scale them both up. Launch Applications Options from the ribbon and select the Sketch tab. From there we will first scale up the Constraints so bump up the value from 1 to 1.5 or 2.
The second area we will adjust is under the General Tab. Look for the Annotation Scale option on the right and change it from 1 to 1.5 or 2.
Simply apply and close the dialog to view you sketch annotations and constrains with the new setting.