Can't add Foreign Key Constraint
It appears you are putting the foreign key on the wrong table.  The column PersonID on the Jobs table should reference the PersonID on the Employee table.

If you are assigning persons to jobs, then your original foreign key should be on JobId.  This would require adding the JobId to the Employees table and removing the PersonId from the Jobs table. 

If Employees can have many Jobs and Jobs can have more than one Employee, then you will want a join table.  It will have foreign keys to both the Jobs and Employees table.  The primary key of the join table will include both the PersonId and JobId.