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* Steps to upgrade to PDFNet SDK v.4.                        *
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1) Download the latest SDK from http://www.pdftron.com/downloads.html and extract 
   the archive to any location (e.g. to C:/PDFNet).

2) Update your project solution to use the new library: 
   [.NET Specifics] Remove the old reference to PDFNet11.DLL and add a new reference 
   to PDFNet.DLL. Please note that the DLL is renamed from PDFNet11 to PDFNet. 
    
   [C/C++ Specifics] Add a path to 'C:/PDFNet/Headers' to your project 'include' 
   directories. Replace the previous PDFNet link dependency ('Linker / Input / 
   Additional Dependencies') with a reference to 'C:/PDFNet/Lib/PDFNetC.lib'. 
   To simplify development you may want to copy the DLL to 'Windows32' folder or to 
   some other location that is included in your application's DLL search path. When 
   you are deploying the application you will most likely want to include PDFNetC.DLL 
   in your application's executable folder. 

3) Instruct the library to run in the production mode by passing the most up-to-date 
   license key in the call to PDFNet.Initialize("...my license key..."). If the 
   license key is not specified, the library will run in the demo mode. If the 
   license key is not valid, PDFNet.Initialize("") will throw an exception.

4) Resolve the compilation errors. 
   The compilation errors will fall in one of the following categories:
   
   A) Simple name changes. 
      For example, PDFDoc.GetPagesCout() should be replaced with GetPageCount(). 
      A listing of symbol changes can be found on 'What's New' page:
      http://www.pdftron.com/net/whatsnew.html
  
   B) Changes in the Iterator interface (e.g. used to traverse pages of fields). 
      Prior to PDFNet v4, a 'for' loop used to traverse all pages in the document 
      may look as follows:
   
      PageIterator itr = pdfdoc.PageBegin();
      PageIterator end = pdfdoc.PageEnd();
      for (; itr!=end; itr.Next()) {
        Page pg = itr.Current();
      }
   
      PDFNet v4 loop would look as follows:

      for (PageIterator = pdfdoc.GetPageIterator(); itr.HasNext(); itr.Next()) {
        Page pg = itr.Current();
      }
   
      The following code snippet used to fetch the first and fifth page:
   
      Page first_page = pdfdoc.PageBegin().Current();
      Page fifth_page = pdfdoc.PageFind(5).Current();
     
      can be rewritten as follows:
     
      Page first_page = pdfdoc.GetPage(1); // or pdfdoc.GetPageIterator().Current(); 
      Page fifth_page = pdfdoc.GetPage(5);
      if (fifth_page != null) ...
   
      Similarly a code snippet used to traverse all form-fields in a PDF/FDF document
      would look as follows:
   
      ' Assuming VB.Net:   
      Dim itr As FieldIterator = doc.GetFieldIterator()
      While itr.HasNext()
        Console.WriteLine("Field name: {0:s}", itr.Current().GetName())
        itr.Next()
      End While
 
   C) Changes in the low-level SDF/Cos API. The SDF/Cos API is refactored to simplify 
      coding and thus reduce errors during development. The updated API is the same 
      in all programming languages, which also simplifies porting code from one 
      language to another. Finally, the new SDF/Cos architecture will allow PDFNet SDK 
      to deliver further performance improvements in upcoming PDFNet v.4.x releases. 
   
      For example, the following code snippet used to create a text annotation using 
      the SDF API:
   
      Obj text_annot = doc.CreateDict();
      text_annot.Put("Subtype", doc.CreateName("Text"));
      text_annot.Put("Open", doc.CreateBool(true));
      text_annot.Put("Contents", doc.CreateString("The quick brown fox ate the lazy mouse."));
      text_annot.Put("Rect", Rect.CreateSDFRect(266, 116, 430, 204));
      annot_array.PushBack(text_annot);
   
      can be corrected as fllows: 
   
      Obj text_annot = annot_array.PushBackArray();
      text_annot.PutName("Subtype", "Text");
      text_annot.PutBool("Open", true);
      text_annot.PutString("Contents", "The quick brown fox ate the lazy mouse.");
      text_annot.PutRect("Rect", 266, 116, 430, 204);
   
      For more examples illustrating the use of updated SDF/Cos API, you may want 
      take a look at SDF and Annotation sample projects.
   
   D) In case you were passing Obj 'hints' in the call to pdftron.PDF.Image.CreateImage() 
      or pdftron.PDF.PDFDraw.Export(), please make the following adjustment: 
   
      // Note: The only difference is that mono and gray hint are created in 
      // ObjSet instead of using Obj.Create
      ObjSet hint_set=new ObjSet(); // A collection of rendering 'hits'.
 
      // Initialize render 'gray_hint' parameter, that is used to control the 
      // rendering process. In this case we tell the rasterizer to export the image 
      // as 1 Bit Per Component (BPC) image.
      Obj mono_hint=hint_set.CreateDict();
      mono_hint.PutNumber("BPC", 1);
      draw.Export(page, "mono.tif", "TIF", mono_hint);

      // 'gray_hint' tells the rasterizer to export the image as grayscale.
      Obj gray_hint=hint_set.CreateDict();  
      gray_hint.PutName("ColorSpace", "Gray");
      draw.Export(page, "gray.png", "PNG", gray_hint);
  
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