Add text on every page

Dear,

I have PDF files and I need to add text on every page they have.

The text can be compared to an ID.

This is not a watermark(!) because a watermark spreads out over the center of the page.

On the right margin of any page, I would like to add text rotated 90 degrees clockwise.

What I mean is something a footer or header but on the side of a page instead of top/bottom.

How am I supposed to do this? I assume making use of a DDX file may help me?

I read something about PageOverlay but I cannot see how i can add content to the pageOverlay in such a way as plain text.

Thanks in advance and awaiting a reply!