If every person's salary goes up by $1000.00:
The mean salary goes up by $1000.00.
The person who had the median salary before the raise will be the person who has the median salary after the raise and, since that person's salary went up by $1000.00, the median salary goes up by $1000.00
The person who had the lowest salary still has the lowest salary, but it is $1000.00 higher.
Similarly, the person who had the highest salary still has the highest salary, but it is also $1000.00 higher.
Finally, the quartiles of the salary distribution also increase by $1000.00.