using (PdfReader reader = new PdfReader(fileName))
            {
                using (PdfDocument pdfDocument = new PdfDocument(reader))
                {
                    for (int i = 1; i <= pdfDocument.GetNumberOfPages(); i++)
                    {
                        string pdfContentString = PdfTextExtractor.GetTextFromPage(pdfDocument.GetPage(i));
                        MessageBox.Show(pdfContentString);
                    }
                }
            }

using (PdfReader reader = new PdfReader(fileName))
            {
                using (PdfDocument pdfDocument = new PdfDocument(reader))
                {                    
                    IEventListener strategy = new ImageRenderListener(imageFileName);
                    PdfCanvasProcessor parser = new PdfCanvasProcessor(strategy);
                    for (var i = 1; i <= pdfDocument.GetNumberOfPages(); i++)
                    {
                        parser.ProcessPageContent(pdfDocument.GetPage(i));
                    }
                }
            }


public class ImageRenderListener : IEventListener
    {
        string format;
        int index = 0;
        public ImageRenderListener(string format)
        {
            this.format = format;
        }

        public void EventOccurred(IEventData data, EventType type)
        {
            if (data is ImageRenderInfo imageData)
            {
                try
                {
                    PdfImageXObject imageObject = imageData.GetImage();
                    if (imageObject != null)
                    {
                        File.WriteAllBytes(string.Format(format, index++, imageObject.IdentifyImageFileExtension()), imageObject.GetImageBytes());
                    }
                }
                catch
                {                    
                }
            }
        }

        public ICollection<EventType> GetSupportedEvents()
        {
            return null;
        }
    }