I am using PDFedit 0.4.1 (under openSUSE, but since the rpm was not specific, this should apply for other OS's too).

It seems to me that there's no need to select the edited text and click back on the main window.

Once the text to be changed is selected, it is enough to change the text as it appears in the property editor at the bottom right.

 Press F5 to refresh and the new text should already be in place.

Jack