How to Create a 90 Degree Watermark on a PDF

Question

I want to create an angled (90 degree) watermark on pdf. Any Ideas?

Launching the application: A-PDF Watermark
In the main window, click "add text watermark" icon, then will open the New Text Watermark configuration window, you can configure the text watermark properties here, the text properties you enter here is actually the text that will appear as the PDF watermark, for example: "for public only", you can choose a rotation angle (90 degree) from "Text Effect" properties
In the watermark list window, marking the watermark items checked
Once you set the desired options for the watermark, you can click OK to save it