Function has_xfa 

pub fn has_xfa(document: &PdfDocument) -> bool

Returns true if the document has an XFA template packet.

Only an active /AcroForm /XFA entry counts here. Orphaned XFA streams left behind after flattening should not trigger another flatten/render pass. XFA PDFs without a template are treated as non-XFA (they have no content to flatten), so this returns false for those documents.