Hi Jen,
At present, we have support for SfPdfViewer control in WinRT only and it does not works on Windows Universal App. We have logged Feature request on your requirement and it will be available in any of our upcoming releases. We usually have an interval of at least three months between releases. The feature implementation would also greatly depend on the factors such as product design, code compatibility and complexity.
Attached a simple SfPdfViewer WinRT sample with MVVM binding for your reference.
Attachment: http://www.syncfusion.com/downloads/support/forum/118578/PDFViewerWintRT1904660307.zip
Please, let us know if you need any further assistance.
Thanks,
Uthistran S.