System 7: Publish and Subscribe vs. Copy and Paste

Copy and Paste are useful when you want to move data between documents and
applications and you want separate copies (versions) of the data in each
place. Publish and subscribe maintains a connection, so that the
"subscribers" always reflect the current data in the "publisher."

For example, if you want a fixed version of a document, like a
"Report-Draft 3," then you could copy and paste into your document.
However, if you want your document to always reflect the most recent
version of "Report," then you would choose publish and subscribe.