Steps to reproduce the issue:
1) Launch Adobe Acrobat Pro DC.
2) Select File > Create > Blank Page.
3) Select Tools > Rich Media.
4) Click Add Button on the toolbar
5) Click anywhere on the document to create a command button.
6) In the newly created button, click the All Properties link.
7) In the window that opens, click the Actions tab.
9) Click the Add button.
10) In the window that opens, type any text and then move the cursor to the beginning of that line.
10) Press the TAB key.
11) The text moves to the right 4 spaces, as it should, but notice the focus is now on the OK button.
12) Press TAB again and see the focus move to the Cancel button.
13) Click back in the Editor at the beginning of your text and press TAB again. Notice that the text moves another 4 spaces to the right, as it should, but once again the focus has moved to the OK button. This make formatting ones code ridiculously difficult.
Please fix this bug asap.