Like the word processor, the spreadsheet feature is also limited in the free version. Pick up the paid version for a much more feature-rich spreadsheet app.
Screen capture by Wally Bahny for TechRepublic
Saw your recommendation and bought Document 2. NOT WORTH it! Emailed test doc was sent as .txt - no formatting. Had to copy and paste formatted text into email to retain formatting - sort of. 12 pt Helvetica ended up as 9 point in the test email received. Recording function was flaky and crashed the app. I then went to write a review of the app, and guess what - I couldn't post it. But I Tweeted my displeasure! Now I want to find a way to get my money back!