There is logged a feature request about the PDF Viewer control in our public feedback portal.
I am sending you a link to the item: PDF Viewer control.
You could subscribe to the item in order to track its progress and get notified by email for any status changes. I am happy to share that the control is planned for R2 2023 release. You can review the Telerik UI for .NET MAUI Roadmap for what's coming in 2023: Roadmap: What's Coming in 2023?
I hope this helps. Let me know if you have additional questions.