Update JavaDoc in PdfVersionImp.java

Author: andreasrosdal

openpdf-core/src/main/java/org/openpdf/text/pdf/internal/PdfVersionImp.java

@@ -61,6 +61,8 @@
 /**
  * Stores the PDF version information, knows how to write a PDF Header, and how to add the version to the catalog (if
  * necessary).
+ * 
+ * For OpenPDF 3.0 this was updated to support PDF 2.0, and specifying PDF version using String "2.0" instead of char.
  */
 
 public class PdfVersionImp implements PdfVersion {