You can use the .exe file in the bin\Debug folder.

-usage

  Print the usage information.

-split

  Please use "PDFSplitMerge.exe -split [SourceFile] [Pages] [OutputFolder]", DO NOT contain any space in [Pages].
  For example:
  PDFSplitMerge.exe -split c:\Users\foo\Desktop\bar.pdf 1,2,3-4 c:\Users\foo\Desktop\

-merge

  Please use "PDFSplitMerge.exe -merge [File1] [File2] ... [FileN] [OutputFolder]"
  For example:
  PDFSplitMerge.exe -merge c:\Users\foo\Desktop\bar.pdf c:\Users\foo\Desktop\bar2.pdf c:\Users\foo\Desktop\

iTextSharp.dll can be downloaded here http://sourceforge.net/projects/itextsharp/