1. The correct form is "boss's document." When indicating possession for a singular noun ending in "s," you add an apostrophe and an "s" after the noun. For example, "The boss's document is on the desk."

2. The correct form is "students' library." When indicating possession for a plural noun, you add an apostrophe after the noun. For example, "The students' library has a wide range of books."

In both cases, the possessive form is used to show that something belongs to or is associated with the noun mentioned.