When you are preparing to send a highly sensitive corporate document or a massive portfolio of original photography to a client, you often need to overlay a semi-transparent “CONFIDENTIAL” or “DRAFT” watermark across the center of every page to prevent unauthorized distribution. You do not need expensive software like Adobe Acrobat or Photoshop to do this. The built-in macOS Preview application contains a robust text tool that allows you to instantly drop custom, semi-transparent watermarks directly onto any PDF or image file.
How to Add a Text Box
To create a watermark, you must first create a standard text annotation.
- Double-click the PDF or image file to open it in Preview.
- Click the Show Markup Toolbar button at the top-right corner of the window (the icon shaped like the tip of a pencil).
- In the new toolbar that appears, click the Text icon (a square containing a capital letter ‘A’).
A small text box containing the word “Text” will drop directly into the center of your document. Double-click the word and type your watermark (e.g., “CONFIDENTIAL” or “DO NOT DISTRIBUTE”).
How to Format the Watermark
A tiny, black watermark is easy to ignore. You need to make it massive and highly visible.
- Highlight the text you just typed inside the box.
- On the Markup Toolbar, click the Text Style icon (an italicized ‘A’).
- A typography menu will drop down. Change the font to a thick, bold typeface (like Impact or Arial Black).
- Use the size dial to increase the font size to something massive (e.g., 90pt or 120pt).
- Change the text color to a stark Red or bright Grey.
Click and drag the massive text box so it sits directly in the absolute center of your document.
How to Make the Watermark Transparent
If your massive red text is 100% opaque, it will completely obscure the actual text or photography underneath it, making the document unreadable. You must drop the opacity so the watermark becomes semi-transparent.
- Ensure your massive text box is selected (you will see the blue sizing dots around the border).
- Click the Text Style icon on the toolbar again to open the typography menu.
- Click on the Text Color box to open the advanced Apple Color Picker.
- At the absolute bottom of the Color Picker window, you will see an Opacity slider.
Click and drag the Opacity slider down to 30% or 40%. Your massive red text will instantly become a ghostly, semi-transparent overlay. It remains highly visible to the reader, clearly marking the document as confidential, but it allows the underlying text and images to bleed through perfectly. Press Command + S to permanently bake the watermark into the file.