Is there a way to have a watermark WITH a dynamic time stamp included?

Our client rep has asked if we can create PDFs (generated from our web app) that not only include a watermark (which we now have using a png image), but a watermark that INCLUDES a dynamic timestamp.

I know we can add these separately, but he wants the watermark itself to be dynamically timestamped.. I know this cannot be done via an image like a png, but is there any other way to do this in a PDF?

Thanks!