In British English
p. stands for 'page' and
pp. 'for pages', so Ant is correct when he says that the plural of
p. is
pp. Here is an example from a book, and below the definition from
a dictionary.
p (PAGE) noun [ C ] plural pp
WRITTEN ABBREVIATION FOR page (PAPER)
See p. 27.
The references are on pp. 256-264.