What can I customize?

The text, opacity, font size and color — stamped diagonally across every page.

Can the watermark be removed later?

It becomes part of each page's content — not trivially removable, but not cryptographic protection either. For real protection, also use Protect PDF.

No — watermarking runs entirely on your device.

Stamp DRAFT, CONFIDENTIAL or any text diagonally across a PDF's pages — opacity, size and color control, no upload.