When you export a pdf-file from InDesign (as an interactive pdf), there should be an option for watermarks.
With this option you could save time because you don’t have to use Acrobat afterwards or create a new layer in InDesign.

In Acrobat this option is already available, but with more opportunities (you don't need so many). It would be enough to have the following possibilities:
- „text of your choice“
- text scale
- text opacity
- text angle (0°, 45°, 90°)