The most effective end-user documentation will be customised guidance and instructions you provide for the label names and configurations you choose. You can use the label policy setting Provide users with a link to a custom help page to specify an internal link for this documentation.

In Office apps, users can then easily access your customised help from the Sensitivity button, Learn More menu option. If you don't specify a link in the policy setting, users don't see this menu option in their apps.

From the Microsoft Purview Information Protection file labler in Windows File Explorer, users can access the same customised help from Help and Feedback > Tell Me More in the file labeler dialogue box.

You can use the following resources for basic instructions:

If your sensitivity labels apply encryption for PDF documents, these documents can be opened with Microsoft Edge on Windows or Mac. For more information, see View protected PDFs using Microsoft Edge on Windows or Mac.