unable to check if a PdfDocument has an AcroForm inside

[fedebona]

Reporting an Issue Here

If I open a PdfDocument
PdfDocument inputPDFDocument = PdfReader.Open(pdfFile, PdfDocumentOpenMode.Import);

I'm not able to check if it has an AcroForm inside.

Expected Behavior

I should be able to check something like
inputPDFDocument.AcroForm != null

Actual Behavior

inputPDFDocument.AcroForm raises an invalidoperation exception

Steps to Reproduce the Behavior

bool hasForm = (inputPDFDocument.AcroForm != null && inputPDFDocument.AcroForm.Elements.Count > 0);
//unwanted Exception raised