[majora2007]

I haven't seen this in the real world or the tooling to back it up. Currently, Calibre is the only software that writes metadata that pulls from online sources.

I'm sure Adobe Acrobat also supports, but that's not used in the scene.

[swiftcoder]

Feels like a very big gap in the OSS world then. The PDF spec supports multiple standards for metadata, Acrobat has workflows for all of them, and Adobe sells into a bunch of verticals (such as public libraries) that rely on this functionality heavily.