According to the description for Spire.PDFViewer NuGet package on the official site, it mentioned that “With Spire.PDFViewer, developers can create any WinForms application to open, view and print PDF document in C# and Visual Basic on .NET”. It is a free version for .NET.
For the version for WPF, you need to buy download the Spire.PDFViewer Pack from below link, which contains Spire.PDFViewer for WPF components.
http://www.e-iceblue.com/Introduce/word-viewer-wpf-introduce.html#.V8Uzrih94z4
After installing, please choose the Spire.PdfViewer.Wpf.dll from C:\Program Files (x86)\e-iceblue\Spire.PdfViewer\Bin\WPF4.0. Then you can add PDFViewer controls into Toolbox.