Use File > Info to quickly unprotect multiple worksheets [Quick tips] -

Ever had a workbook with multiple protected worksheets? May be you are enterprise architect at Death Star or chief strategist at Mordor and got all the plans in a tidy little but protected workbook. Of course, you hate having to unprotect many of the worksheets every time you have a new evil plan for world domination. Don’t you worry, you can use this handy little trick to unprotect en masse.

Just open the workbook
Go to File > Info
Right on the top, you can see all protected worksheets and a link to unprotect them.
Click to unprotect the ones you want to.
Done.

Here is a quick demo of the process.