You can set Pages to flag spelling errors as you enter text. You can also quickly look up the definition and suggested spellings of a word.
Tap 
, then tap Settings.
Turn on Check Spelling.
Misspelled words are underlined in red.
Tap a misspelled word, then tap a suggested spelling.
If you don’t see suggested spellings, tap the right arrow, tap Replace, then tap the correct spelling.
Tap , then tap Settings.
Turn off Check Spelling.
If you don’t want words to be corrected as you type, turn off autocorrect. See the task below for instructions.
When autocorrect is turned on in iOS Settings, misspelled and unknown words are automatically corrected as you type. Turning off autocorrect applies not only to Pages, but to other applications where you type text, such as Mail.
Tap Settings on the Home screen, then tap General.
Tap Keyboard, then turn off Auto-Correction.