As far as I know, everything printable can be done so, as long as one doesn’t distribute it without author’s consent. Paywalls, for example, but then they are not free. Music scores are tricky as no one should be using them in Church or anywhere else without permission.
If the items are published with a Creative Commons license you’re fine. If it’s copyrighted and you’re using it for education it probably falls under fair use. If it’s behind a paywall and you’re circumventing that, for instance with SciHub, you’re violating copyright. Just pay attention to whether it’s coming from a legitimate site.
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