A watermark does two jobs and neither is security. It stops a draft being read as final, which is the mistake that actually happens. And when each copy carries the name of the person it went to, a document that turns up where it should not says which copy it was, which changes how carefully people treat what they are sent. Both are done here, on your machine, without uploading a document you are worried about circulating.
Drop a PDF here, or
Anything in the second line that identifies who a copy went to is what makes a leaked copy traceable. A date alone does not.
Drawing...
A watermark is not a lock, and anybody telling you otherwise is selling something. It is drawing on a page. Anyone determined can take it off with the same sort of tool that put it on, and a screenshot of the middle of a page loses it entirely. What it does is stop a draft being mistaken for final, and make a leaked copy identifiable, and both of those are worth having. Treating it as protection is how a document ends up somewhere it should not have gone.
The name is the part that matters. CONFIDENTIAL across a page tells a reader something they already knew. The name of the person the copy went to tells you, later, which copy it was. That is the difference between a document that leaks anonymously and one where the question has an answer, and people read a document differently when their own name is across it.
The line along the bottom survives things the big one does not. A photograph of one page, a screenshot of a section, a page printed and scanned back in: the diagonal words across the middle often end up cropped out and the small line along the foot of the page does not. It carries the page number too, which is how anyone can tell whether they are looking at all of something.
Behind the text or in front of it. In front is more visible and harder to ignore. Behind reads better and does not obscure a table. Neither is more secure than the other, because neither is secure; choose whichever the document is easier to read with. On a scanned page there is no text to go behind, so the setting does nothing.
It happens in this tab. The documents people want to watermark are the ones they are worried about circulating. Uploading one of those to a website in order to write CONFIDENTIAL on it is a strange order of operations. Turn the network off and this page works exactly as it does now.
No. Nothing will. A watermark is a deterrent and a label, not a control: it makes casual sharing feel traceable and it stops a draft being read as final. Anyone who wants the words off can get them off, and anyone photographing a screen never had them in the way.
Not in one pass, deliberately: producing fifty files at once is how the wrong name goes on the wrong copy. Put one name in, save it, change the name, save again. It takes a few seconds a copy and the result is right.
No. The words and the layout are untouched; the watermark is drawn over or under them as page content. Anything that could read the document before can still read it, which is also why a watermark is not a protection.
Any change to a signed file breaks the signature, watermarking included. Stamp the copy first and sign afterwards, in that order, or send the signed original and a watermarked copy separately.
Usually because it is behind a page that is a full-page scan or image, which covers it. Untick the box that puts it behind the text and it will be drawn on top instead. The line along the bottom is always drawn on top for that reason.