Represents the "UF" entry of the embedded file set dictionary object.

It is an optional entry defined as part of the PDF 1.7 specification.

It contains an EmbeddedFileStreamElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; page 103.

The UF entry in an embedded file set maps the UF path key to an embedded file stream reference. This is the Unicode-path equivalent of the F entry.