Thank you for your update.
We are unable to reproduce the issue of "A first chance exception of type 'System.FormatException' occurred in Syncfusion.SfPdfViewer.WinRT.DLL". Please find the sample in the link below with which we tried to reproduce the issue, please modify this sample or provide us a simple sample with which this issue could be reproduced. This will help us to further investigate on this.
Please, let us know if you need any further assistance.