The highlighter is like the high lighter you used in school, it covers the text but still allows one to read the text.
If you want to remove the data or cover it so it is unreadable, also known as redaction, then you need to remove the data and fill-in the space of the removed data then use the Redaction in Acrobat Professional. If you want just a white cover over the text but still allow the text under the cover to located with find, search, and to be cut and pasted , then create a form field with the color white for fill. You could also change the color of the text to white.