This from the Help pages of Pages. Surprised you didn't find it there.
Make characters superscript or subscript
You can adjust the baseline of characters to make them superscript or subscript. A trademark symbol is superscript because it's raised above the trademarked term. In a chemical formula, the number of atoms is subscript because it's lowered below the symbol of the atom. In Pages, you can make selected text superscript or subscript, then tweak the baseline of the text by small increments if you want.
Select the text you want to make superscript or subscript.
In the Text pane of the Format inspector, click the Style button.
In the Font section, click Advanced options button, then choose Superscript or Subscript from the Baseline pop-up menu.
To adjust the placement, use the arrows to change the Baseline Shift value.
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