
This will add an annotation (or comment), it will not add static PDF text as you can do with the "Add Text" tool. For both of them, you can select the background color (again, using the properties toolbar as explained before). The one on the left will not add a box around the text you type, the one on the right will have a box around the text. Click on the "Comment" item in the right hand pane, this will bring up a new toolbar: Which version of Acrobat did you use before you moved to Acrobat DC? How did you add text back then? If you were able to configure a background, I assume it was an annotation or comment that you added. The only difference was that the tool used to be called the TouchUp Text tool. Whatever is behind that text will be used as the background for your text - this has never been different in previous releases of Acrobat.

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The "Add Text" tool does not have a background color associated with it, because it is not adding anything besides the text you type.

The "Text Box" is on the Comments toolbar. What you are using is not a "text box", it's the "Add Text" tool.
