How can I add copy stamp for pdf before the deadline?

My PDF needs a copy stamp added before the deadline and I’ve tried a couple things without success on my work laptop. What should I do?

Honestly, the simplest fix is opening it in the free Acrobat Reader if you have it. Just go to Tools > Comment and theres a built-in Stamp tool with COPY ready to use. Saves me all the time when rushing contracts.