Workbook Security If you use a computer, you probably have some Microsoft Excel documents on your Mac or PC that you wouldn’t want other people to find and read. After all, Excel is used by both regular consumers, businesses, government institutions, and millions of other folks all over the world. The best way to keep that information safe is to learn how to password protect an Excel file.
Go to File --> Info --> Protect Workbook --> Encrypt with Password
Protecting a worksheet from being modified, or restricting the modifications to certain users.
Go to Review --> Protect Sheet