You can protect your document by applying password so that unauthorized person can not display as well as modify your document. You can apply two types of passwords:

Password to open the document: If it is applied then you have to give the correct password to open the document, otherwise you cannot open the document.

Password to modify the document: If it is applied then you have to give the correct password to modify the document, otherwise your document is opened but you cannot modify the document. It means that your document becomes read-only.

To apply a password to document:

1. Open Save As dialog box by selecting Save As command from File menu.
3. Click Tools button and choose General Options from drop down menu. Save dialog box opens.
4. Enter first password in Password to open text box and second password in Password to modify text box (if required). NOTE: The maximum length of password is 15 characters.
5. Click Ok button. Confirm Password dialog box opens.
6. Re-enter the password to open and password to modify and click Ok button of Confirm Password dialog boxes one by one.
7. Click Save button of Save As dialog box.