You may not acquire items (kinyan) on Shabbat unless they are needed for that Shabbat or for doing a mitzva. The classic example of doing something for Shabbat is bringing food or drink to a house for Shabbat lunch, which the house owner acquires on Shabbat for Shabbat. Other permissible kinyan on Shabbat:

•  Giving a siddur or chumash to use on that Shabbat.
•  Giving permissible medicine for use on that Shabbat.