You can add a watermark to a PDF on iPhone in Safari without downloading any app. Here is how.
Navigate to pdfeditor.onl/watermark-pdf in Safari.
Tap the upload area and select your PDF from Files or iCloud. Enter your watermark text (or switch to image mode to upload a logo). Set opacity, size, and rotation.
Tip: In landscape mode on iPhone, you get a larger preview of the watermark placement — helpful for checking position before applying.
Tap Apply to All Pages. Tap Download to save the watermarked PDF to your Files app.
Yes. Any iPhone with iOS 14 or later and Safari supports the watermark tool.
Yes — completely free in Safari on iPhone.