The document is opened on your device.
Text or an image, with position, angle and transparency of your choosing.
The watermark is written into the document, not overlaid by the reader.
The file does not leave your device. Thirty-two tools out of thirty-eight.
It should be said honestly: a watermark is a visual mark, not a protection. Someone with the right tools can remove it. It declares the status of a copy, it does not prevent its use — encryption or redaction are the tools for that.
Yes: upload an image and use it as the watermark, adjusting its transparency and position.
Yes, and a batch of up to 20 files counts as one operation against the free daily quota.
It opens in your browser, nothing to install. Five operations a day are free, with no payment details.