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Ditto in Russia, e.g. https://www.litres.ru/. They know that if they don't do that, people will just pirate en masse - they had to compete with pirated books for convenience.

Manning books in the US watermarks their ebooks too (each page have a "property of XYX" on it). Its not DRM or even unsharable, I think it just makes you think about who your sharing with...)

From which reseller / publisher?