footnote-style

footnote-style is a variable defined in `footnote.el'.
Its value is

numeric

Documentation:
Default style used for footnoting.
numeric == 1, 2, 3, ...
english-lower == a, b, c, ...
english-upper == A, B, C, ...
roman-lower == i, ii, iii, iv, v, ...
roman-upper == I, II, III, IV, V, ...
latin == ¹ ² ³ º ª § ¶
unicode == ¹, ², ³, ...
See also variables `footnote-start-tag' and `footnote-end-tag'.

Note: some characters in the unicode style may not show up
properly if the default font does not contain those characters.

Customizing this variable has no effect on buffers already
displaying footnotes. To change the style of footnotes in such a
buffer use the command `Footnote-set-style'.

You can customize this variable.