Install the Astrol.Component.PDFViewer package from the AstrolUI NuGet or reference the project to your solution.
Add the AstrolUi NuGet repository to the NuGet Package Manager Configuration of your Visual Studio.
Source: https://nuget.astrolui.com/v3/index.json (Refer to documentation on how to configure package sources in Visual Studio)
<!-- AstrolPDFViewer Script-->
<script src="_content/Astrol.Component.PDFViewer/js/astrol-pdf.js"></script>