Yes. Type anything up to 60 characters, such as your company name or "Copy for Jane Smith".
No. It's see-through, so the page can still be read. Choose Light, Medium or Strong.
It's part of each page, so it can't simply be switched off, but a determined person with PDF editing software could remove it. For stronger protection, also add a password with Protect PDF.
No. The watermark is added in your browser, on your device.
Find the right tool for your next job.