According to the Dictionnaire historique de la langue française the word pédéraste has been used to mean homosexuel (and not a man who has sexual relationships with adolescent boys only) since the early 20th century.
But I remember the word being used by André Gide in the early 20th century to mean a man attracted by young boys.
In Being and Nothingness (1943) Sartre - the man and philosopher - uses homosexuel to talk about a homosexual and pédéraste between brackets to refer to exactly the same person, the brackets implying the word is derogatory in Sartre's eyes. But it absolutely clear he does not use the word pédéraste to imply an exclusive preference for adolescent boys.
You will find an extract online here. The word pédéraste is used both times to reflect how other people (not Sartre) see the homosexual.
You must keep in mind that in the novel Sartre puts the words in the mouth of his characters, he writes the words but they are not his own words. In the extract I am pointing to Sartre talks about the shame felt by the homosexual. So you must ask yourself as you read: Who says what ? Is it Daniel? Is it another character? Is it the author?
I do not remember if in L'âge de raison Sartre uses the word pédéraste as Sartre, the author, but if he does, he probably did not try to stress Daniel liked younger men (even if he did). And we must also remember that Sartre fought for gay & lesbian rights (as we say nowadays) and I presume he would not use the words lightly.
The word pédéraste is hardly used nowadays in France. According to the Dictionnaire culturel en langue française it was superseded by homosexuel in the 1950-60s. Only the short form pédé is used nowadays as a very derogatory term and a severe insult.