Kutools has become quite famous now a days, it had many functionality that excel lacks.
If I modify a file using Kutools and send it to someone will the other user be able to use it, who does not have Kutools
If you use Kutools to change the worksheet the changes will stay in the worksheet wherever it goes
If you add any functions, that are Kutools specific, they will either
1. If the function is loaded into the file, the function will continue to follow the file around
2. If the Function isn't included in the file, return an error when next you open the file on a pc without kutools