We are experimenting with a tool that watermarks the PDFs of papers published at CEUR-WS.org. The watermark is imprinted in the left margin of the first page and consists of the URL of that paper, e.g. “CEUR-WS.org/Vol-2345/paper1.pdf”. The watermark allows readers to trace back the original location where the paper was published. It does not change the fact that the paper is copyrighted by its authors, and published by its editors. That information can be added by authors/editors as a footnote.
The automatic watermarking will likely be the standard procedure from mid 2018 onwards or earlier.