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Need to how to transfer an assembly file with its parts to other user at a different company?
If they have Creo as well (and at least the version you have), open assembly and use File > Backup saving it into an empty directory. Then zip this directory which is now containing everything needed.
If they have another CAD system, you can only exchange model geometry by standard interfaces like IGES or STEP, found under File > Save As and changing the file type.