Documents and spreadsheets created in Microsoft Word and Excel can be password-protected easily. To do this in Excel, open the relevant document, then click File, followed by Save As.

In the Save As dialogue, choose the file save location, then click the Tools button and pick General Options. Type the required password (or passwords - you can specify one each for permission to open or modify the file).

Re-enter the password(s) when prompted then click Save and the file will prompt for the password(s) the next time it’s opened. In Word the process is much the same, but select Security Options from the Tools menu in the Save As dialogue box.