There is no option to add text box in edit tool, So, I assume you are talking about the text box that you have you added using comment tool .
If yes, Please try once to change the properties of the text in text box under the comment tool and let us know if it works.
Thanks Meenakhi - I may not have explained the nuances of the language you use to describe the obvious! Bottom line, no matter HOW I get into a text box, once the text itself is highlighted, I cannot CTL-E to get the properties box. Further, if I open the properties box BEFORE highlighting the text within the box, I cannot change the properties of the text (the properties are shown but all options are greyed out). This just started after the latest update was applied: I have been using Acrobat since version 1.0 so I am pretty familiar with the gyrations that have been applied over the many years and how to edit text, both within a text box and as straight text.
If you still don't understand the problem, please let me know how to contact you directly and I'll walk you through it. Could be something peculiar about my setup (perhaps you don't use Win 10 very often) but I should be able to help you with whatever diagnostics you want to go through (37+ years as a Software Engineer).
Thank you - so, you now MUST have the comment tool open to use the textbox (unless you want to use the default formats). Used to be, I could put the textbox in the quck tools bar and then CTL-E to get the text properties. Now, even if you put the text properties tool in the quck tools bar, you cannot get the text properties UNLESS THE COMMENT BAR IS ACTIVE. Guess I'll have to live with the fact you keep limiting the user's abilities every time you change the program.
We have released an update today that fixes the Properties Toolbar issue and you can now continue to use it outside the Commenting app as well. Please open Acrobat or Reader DC and visit Help > Check for updates to make sure you are on the latest patch.
Details about the release: https://helpx.adobe.com/acrobat/release-note/acrobat-dc-august-02-2016.html
Please let us know how it goes.