A paradigm in a literary context means a typical example of something. Superman is a paradigm of superheroes; an apple is a paradigm of fruit. It is sort of the first thing that comes to mind. Satan and Eve are both paradigmatic rebels, because they are two of the earliest “recorded” and most famous examples of rebellion in the Western canon.
Satan and Eve in Paradise Lost both live within hierarchies they choose to break out of. In Satan’s case, as the angel Lucifer, he felt subjugated by both the Father and Son (God and Christ). Being one of the most powerful and beloved angels in Heaven was not enough for him, leading to possibly the most famous line of the epic: “Better to reign in Hell than serve in Heaven.” In Eve’s case, she lives in the hierarchy of Eden. She is above all the animals, but she is implicitly below Adam and, of course, not in the same stratosphere as God, Christ, and the angels. In Eve’s defense, she is swayed to eat the apple by Satan disguised as the snake, who tells her that he ate it (which is why this snake can talk) and suggests that God wants her to eat the apple, because it will cause her to display her independence. The talking snake does a good deal to sway Eve. It made her believe that the hierarchy of Eden was malleable and not strict, since this snake was able to rise up in the world and gain speech.
It is worth noting that both Eve and Satan fell from much better positions (Heaven and Eden) to much lesser ones (Hell and Earth) by virtue of their rebellions.