Watermarks are a conversion tactic: freemium editors stamp your document so that you'll pay to remove the stamp. That's a bad deal when the document is a job application, a signed contract or an invoice going to a client — a “edited with free version” banner is unprofessional at best.
EditFreePDF has no premium plan, so the incentive doesn't exist. The editor runs in your browser, costs nothing to operate per-file, and outputs exactly what you made: your pages, your text, your signature — nothing else. If you've been hunting for “free PDF editor no watermark” after getting burned, this is the behavior you were expecting all along.