Normally you would not need to call this method directly because calling only PreCacheDocument(FileProvider, DocumentCacheOptions) method handles the conversion chain: Source -> PDF -> XPZ.
public FileCacheItem GetOrAddXpz(
DocumentCacheInfo cacheInfo,
string attachment = null
)
Public Function GetOrAddXpz (
cacheInfo As DocumentCacheInfo,
Optional attachment As String = Nothing
) As FileCacheItem
The attachment name in a PDF Portfolio file, can have folder information e.g. "Subfolder/File.docx". Also nested attachments can be accessed with "|" separator e.g. "FirstLevel.msg|SecondLevel.docx".