Stamp a text watermark across every page. Drag it anywhere on the live preview and resize its width and height freely, then download, all in your browser.
Drop a PDF and position your watermark on a live preview of the first page. Drag it where you want, resize its width and height with the corner handle, set the opacity, angle and color, then stamp it across every page.
Because the preview and the watermark are both rendered in your browser, the document is never uploaded. What you see in the preview is exactly what gets saved.