If you download your tax forms can you still go back and file electronically ? According to turbo tax front page you can

Yes, you can still switch to e-file as long as you didn't mail in your filing copy. Here's how to do that:

1. Sign in to your TurboTax account.
2. Select Add State.
3. Select Review from the left-side menu  (expand your browser window if you don't see this, or select the menu icon in the top left corner).
4. Address any details that come up.
5. Select File.
6. On the Just one more step screen, follow steps 1 and 2 if you haven't already.
7. Select the Start to the right of Step 3.
8. On the Let's get ready to e-file screen, select I want to e-file.
9. Follow the instructions to e-file your return.