[PDFNet] Could not load file or assembly 'PDFNet.dll' ' when using PDFNet for .NET 4.x

The PDFNet x64 library is for targeting frameworks 2.0 - 3.5. Since your building .net 4 or 4.5, you should use PDFNet for .Net 4.


You can see the libraries and the frameworks they target at this link

If there is some reason to use the .Net 2 assembly, the following article might help.