Acrobat 2020 using highlighter on an object not text

Hello,

One of our users is trying to use the highlight tool in Acrobat 2020 to highlight an object. They have a PDF document that has a CAD drawing with text. They want to use the highlight tool to highlight walls to be worked on. But the highlighter only selects the text that is near the wall to highlight. How can I change the setting to let the highlighter work on everything, or is there a diffrent tool they should use that will work like the highlighter?