Including technical steps like using checksums would require knowing the checksum provided by the magazine. If they don’t provide it, then it's hard to verify that way. So maybe that's a point in the advice—only use official sources where such checks are possible.
I think Lui Magazine is from South Korea. Wait, no, maybe it's a Chinese magazine. Let me check that. Yeah, I recall some fashion magazines from China having similar names. Alternatively, there's a French magazine "Lui" too. Wait, no, "Lui" in French might mean "He" or something. Maybe they are using it as a name. I might need to verify the correct origin of Lui Magazine. lui magazine pdf better verified
I should also mention digital rights management (DRM) if the PDF is protected by any. For example, some magazines use DRM to control access, which can be part of verifying that the PDF is legitimate and legally obtained. Including technical steps like using checksums would require