When exporting a document with the .NET Framework implementation, only subsets of the used fonts are embedded in the document. This is currently not available in the Silverlight implementation, and it most probably won't be available in the .NET Standard implementation, as the current implementation is dependent on the WPF font classes. Provide API to plug similar logic when using different platforms as well.
This item wil handle the TrueType OpenType Font format. For the Compact Font Format (CFF) please follow: Export subset of Compact Font Format (CFF) fonts for platforms different than .NET Framework