Referencing correctly is important in order to avoid plagiarism or academic dishonesty, using quotation marks if it is an exact citation and always indicating the source both in the citation and in the paraphrase. Avoid "inventing" citations, i.e. quoting authors who have not been read, or attributing ideas or conclusions to authors they do not actually belong to.
Metadata can be included in texts, and images or watermarks in documents, as a way of preventing plagiarism. Including the citation of the work in the document itself is also recommended, as this will help ensure it is done correctly. This also prevents the text from being "orphaned" and from reaching the reader without any context, something which happens, for example, when we find text via a search engine.