How can you protect a worksheet in Excel from unwanted changes?

The most effective method to protect a worksheet in Excel from unwanted changes is by locking the cells and protecting the sheet. When you lock cells, you prevent any modifications to the content of those cells, and by protecting the sheet, you ensure that users cannot unlock those cells or make changes at all.

This approach allows you to selectively control which parts of the worksheet can be edited, providing a robust security layer around your data while still allowing users to interact with the rest of the worksheet if desired. Locking cells is done in the cell format options, and protection can be enabled through the Review tab in Excel.

By contrast, hiding the worksheet merely makes it invisible but does not prevent changes if someone knows how to unhide it. Saving as a PDF is a way to share or distribute the worksheet without granting edit privileges, but it does not provide any protection in the context of the original Excel file where changes could still occur. Conditional formatting changes how data is visually represented but does not provide any protection measures against altering the actual data.