Assuming you just want to display a bounding box around or instead of each object, you can do this with Draw types.
Drawing a bounding box instead of the object:
You could set Viewport shading to Bounding box to draw the bounds of each object:

A comparison between Solid and Bounding box:

To do this for one object only, you can set this in Properties > Object Display > Maximum draw type:


Drawing a bounding box around the object:
This can be done by enabling Bounds with the Maximum draw type still higher than Bounds:

This looks like this:

You could do this for many objects by:
Select the objects for which you want to enable Bounding box
Enable Bounds in Object > Display
Right click on the Bounds option and select Copy to selected:

