If you are referring to the character limit then no there is no way to change that after a debate begins. You and your opponent both get the same limitations.
You may ask your opponent for permission to use a Google doc to bypass the character limit but doing so without express written permission from your opponent would be very bad conduct (because, again, they have the same limits you do) and most voters would rightfully give your opponent the win for such a hypothetical breach of etiquette.
If you are not talking about character limit and I have somehow misunderstood your question please clarify and tag me and I shall try to provide a better answer.
