davedran,
After a case has a status of "COMPLETED" or "CANCELLED" there is no easy way to restart the case. You can write directly to the database with a trigger. See:
http://wiki.processmaker.com/index.php/ ... ing_a_Case
You would need to create a process with a DynaForm were the user can enter the case number and the trigger which is fired after the DynaForm would change the status of the specified case.
Another way to do it is to use PMFNewCase() to start a new case. Then you can call
Cases::LoadCase() to get the variables from the old case and use PMFSendVariables() to send those variables to the new case, but you can only begin the new case at a starting task, so you might have to redo some tasks in the new case to get back to the original point.
If you aren't a programmer and this is too complicated for you to implement, then I recommend that you simply pause the case. Then the assigned user or Process Supervisors can unpause the case.