US/Australian English in Pages

[auntyj]

I'm proofreading a long document, I’m Australian but the author is American. Is there any way to change the language in Pages, so spellcheck doesn’t underline every US spelling of a word? I'm missing the genuine errors amongst all the ‘misspelt' words.
Even changing the language of my entire iPad didn’t solve it!
iPad Pro, running IPS 11.2.6.
Thanks