Hi @Chong, Ryan
Based on my experience, if you are working with a document that is saved to a library on a SharePoint site, you could insert a label into your Office file when you save or print it. You could find the details about how to manually insert label from this article's Insert a label manually. But this feature has been discontinued in SharePoint 2013 and later versions.
So if you could not do above setting, as a workaround, we also recommend you try to create the folder to make a difference for each documents.
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