>> >> (prin1 '(("'A" . [?Á])
>> >>          ("'E" . [?É])
>> >>          ("'I" . [?Í])
>> >>          ("'O" . [?Ó])
>> >>          ("'U" . [?Ú])
>> >>          ("'Y" . [?Ý]))
>> >>        (current-buffer))
>> >
>> > Why do you have to use prin1?
>>
>> Actually I need to use pp-to-string to pretty-print the list,
>> but pp-to-string calls '(prin1 object (current-buffer))'.
>
> prin1 accepts a function as its 2nd argument; can you use that?

I tried to use a function in the 2nd argument, but it's called
for every digit of the integer that represents a character,
so I don't know what to do with these digits.

However, do you think something like the following is a good idea?

Let-binding a new variable 'print-integers-as-chars' to t:

(let ((print-integers-as-chars t))
  (pp '(("'A" . [?Á])
        ("'E" . [?É])
        ("'I" . [?Í])
        ("'O" . [?Ó])
        ("'U" . [?Ú])
        ("'Y" . [?Ý]))
      (current-buffer)))

prints integers as characters:

(("'A" .  [?Á])
 ("'E" .  [?É])
 ("'I" .  [?Í])
 ("'O" .  [?Ó])
 ("'U" .  [?Ú])
 ("'Y" .  [?Ý]))

with this patch: