Go to Document > Watermark...
This opens the Watermark editing window. In this window you can enter text that will appear on all printed and PDF pages:
Enter the watermark text and click OK to return to the script. To preview how the watermark will look, go to File > Print Preview:
Once a watermark has been added to a script and the script has been exported as a PDF, the watermark cannot be removed from the PDF.
To remove a watermark from a Final Draft script, go to Document > Watermark, clear the text box and click OK.
The position, font and size of the watermark text cannot be changed.
To learn more about watermarking your script watch the following video: