Sorry but I've been busy.
OK I combined the two responses immediately above, and made sure that I created a new layer, and then, worked in that layer to write the text.
Then, after closing then reopening it, I used the Move Selected Pixels tool to move the text.
What I saw was that everything I wrote (on that second layer) was moved, not just one word. For example, earlier I typed in "Turkey" and "Saudi Arabia." When I reopened it, I was able to move the text, but I could not simply move one term. When I moved "Turkey," "Saudi Arabia" also moved.
And I see that you can't really edit the text, as has been explained above. At this point, I don't think Paint.NET is the tool I need to use for this particular purpose.
Thanks for bearing with me.