Hi,
I had developed an Xamarin application, in a modal I open a PdfViewer.
PdfViewerPage pdfViewer = new PdfViewerPage(item.IdAllegato, item.Path, item.FlagScaricabile);
Navigation.PushModalAsync(pdfViewer);
I assign a url to the PdfViewer source.
pdfViewer.Source = new Uri(uri);