"unresolved external symbol" or "unable to start"

error LNK2019: unresolved external symbol __imp__TRN_PDFNetInitialize.

You probably have mixed up the 32bit and 64bit versions of PDFNetC. Make sure that the DLL architecture matches the project platform setting.

error: The application was unable to start correctly.

Same as above, but at runtime you have the wrong PDFNetC.dll being loaded.