I also found myself boxed in when using text boxes; I couldn't get the cursor past the last box. The easiest way I found around the problem was:

1. Open a new document
2. Hold down the "enter" key; the cursor will move down the screen, creating blank space (I needed 4 pages of blank space, I created 6 just in case).
3. On the original document, select and copy everything.
4. Go to the new document, place the cursor at the beginning, and paste in the old. You are now free to type around the document.

Hope this helps.