Answer
It is possible. Fred is paid the most and Janice the least.
Work Step by Step
Statement 1:
If Fred is not the highest paid of the three, then Janice is.
Statement 2:
If Janice is not the lowest paid, Maggie is paid the most
From the first statement "If Fred is not the highest paid of the three, then Janice is", we can deduce Maggie is not the highest paid.
But, the second statement says "If Janice is not the lowest paid, Maggie is paid the most". Since we know Maggie is not the highest paid, we can deduce Janice is the lowest paid.
If Janice is the lowest paid, Fred is the highest paid (statement 1).
Then, obviously, Maggie is in the middle.