How to insert text into a page in the browser as a note before saving. in pdf?

Question

Google Chrome

Let's say I want to put some text on the html page, like a note, before I save it to pdf. I know that this is possible if manually through the dev console, if you correct the html code. But, it's inconvenient. It would be convenient to just poke the cursor and start writing.

Is there a way?

Mainly in Firefox.