I am a developer of Docotic.Pdf Library. We use PDF comparison in unit tests for checking that test produces PDF as expected. PDF is a collection of special objects and we compare all PDF objects ignoring some properties like trailer IDs and creator info. This implementation works fine.
You can try the method PdfDocument.DocumentsAreEqual. This method just tell you are documents equal, without specific differences. You may contact us if you need more functionality.
