Please find the NuGet package details below:
https://www.nuget.org/packages/Syncfusion.Pdf.WinForms
https://www.nuget.org/packages/Syncfusion.Pdf.WinForms#dependencies-body-tab
A nupkg file is typically a package file for the NuGet package manager used in Microsoft Visual Studio. To open a nupkg file, you can use any program that can extract the contents of a compressed archive, such as 7-Zip or WinRAR.
with this, you can get the DLL for the requested namespace, and Add the dependency DLL as well in the project to resolve other compilation issues.
We have attached the video demonstration to illustrate this, try this on your end and let us know the result,
https://www.syncfusion.com/downloads/support/directtrac/general/ze/ScreenCapture_4-26-2023_2.22.12_PM.mp4-1445162520
