The second is most specific. There can be no question what you mean here. Your discussion focuses on that one document and nothing else.
The first example is less clear. You probably mean exactly the same thing as you say in the second example, but you COULD mean
a) I have only read the first page, not tried to translate it yet or make any sense out of it, let alone colour in the pictures on it.
b) I have only read the first page, and haven't done the laundry yet.
c) I have only read the first page and I am falling asleep.
But in fact, I'm being pedantic. Both probably mean the same thing. Thank heavens we don't have any phoney rules about split verb phrases (have ^only^ read) like we do with infinitives (to ^boldly^ go), so you can feel comfortable using either one.
Student or Learner