Workbook passwords can be changed or removed by anyone who knows the current password.
Open the workbook that you want to change or remove the password for.
On the Review tab, click Protect Sheet or Protect Workbook.
To remove a password from the workbook, click Protect Workbook, and then click OK without entering a new password.
Please note:
Passwords in Excel for Mac and Word for Mac have a 15-character limit. You cannot open a workbook or document that has been password protected in the Windows-based version of Excel or Word if the password is longer than fifteen characters. If you want to open the file in Office for Mac, ask the Windows-based author to adjust the password length.