public int StartSearch(string text, int pageIndex)
        {
            if (pageIndex < 0 || pageIndex >= pdfViewer1.Document.Pages.Count)
            {
                return -1;
            }
            
            lastPdfFind = null; // class var

            for (lastPdfFindPageIndex = pageIndex; lastPdfFindPageIndex < pdfViewer1.Document.Pages.Count; lastPdfFindPageIndex++)
            {
                PdfText pdfText = pdfViewer1.Document.Pages[lastPdfFindPageIndex].Text;
                lastPdfFind = PdfFind.Find(text, pdfText, Patagames.Pdf.Enums.FindFlags.None, 0);
                if (lastPdfFind != null) // PdfFind.Find() appears to return null if text is not found (undocumented)
                {
                    break;
                }
            }

            if (lastPdfFind != null)
            {
                HighlightSearchResult(lastPdfFindPageIndex, lastPdfFind);
                return lastPdfFind.CharIndex;
            }

            return -1;
        }

        public int FindNext()
        {
            if (this.lastPdfFind == null)
            {
                return -1;
            }

            if (lastPdfFind.FindNext()) // exception here if PdfViewer page was changed manually by scrolling
            {
                HighlightSearchResult(lastPdfFindPageIndex, lastPdfFind);
                //MessageBox.Show("lastPdfFind.CharIndex: " + this.lastPdfFind.CharIndex);
                return this.lastPdfFind.CharIndex;
            }

            return -1;
        }

        private void HighlightSearchResult(int pageIndex, PdfFind pdfFind)
        {
            pdfViewer1.RemoveHighlightFromText();
            pdfViewer1.HighlightText(pageIndex, pdfFind.CharIndex, pdfFind.CharsCount, Color.FromArgb(90, 255, 255, 0));
            pdfViewer1.CurrentIndex = pageIndex;
            var page = pdfViewer1.Document.Pages[pageIndex];
            var ti = page.Text.GetTextInfo(pdfFind.CharIndex, 1);
            if (ti.Rects == null || ti.Rects.Count == 0)
            {
                pdfViewer1.ScrollToPage(pageIndex);
                return;
            }
            var pt = pdfViewer1.PageToClient(pageIndex, new PointF(ti.Rects[0].left, ti.Rects[0].top));
            var curPt = pdfViewer1.AutoScrollPosition;
            pdfViewer1.AutoScrollPosition = new Point(pt.X - curPt.X, pt.Y - curPt.Y);
        }