I am not able to select text pdfiumViewer

Question

I am not able to select text pdfiumViewer after convert from base64 to stream and give it to the PdfIumViewer, Is there any way to enable textSelection.

PdfiumViewer.PdfViewer pdf;

string base64ImageRepresentation = Convert.ToBase64String(byteFile[a]);
var stream = new MemoryStream(System.Convert.FromBase64String(base64ImageRepresentation));
PdfDocument pdfDocum = PdfDocument.Load(stream);
pdf.Document = pdfDocum;