To insert a text or image watermark into a document, follow these steps:

1. Open the file in an Office365 program such as Word, Powerpoint, etc.
2. Go to the menu/ribbon and select ‘Insert’
3. Go to ‘Text’ and type in the watermark message or select an image file
4. Adjust settings such as transparency, font size, position, color, etc.
5. Select OK and it will be inserted into the document