How this works
There is no reliable way to detect an arbitrary watermark automatically, so you mark it once by drawing a box over it on the page-1 preview. We then paint over that same box on every page - either by sampling the colour around it and blending a patch in (best for a logo or text stamp on a plain or lightly textured page), or by heavily blurring the area (safer for a busy background, though the outline may still be faintly visible).
Every page becomes an image
To paint over a mark on every page, each page of the PDF is rendered to a high-resolution image and the result is rebuilt into a new PDF. It looks and prints the same, but the text is no longer selectable or searchable afterwards - keep the original if you need that.
Best results
- Draw the box a little larger than the watermark itself so no edge peeks out.
- "Auto blend" works best when the area around the watermark is plain or gently textured (scanned documents, certificates, letterheads).
- A watermark stamped at the same spot on every page is covered on every page in one pass - that is the common case.