var selInfo = pdfViewer1.SelectInfo;
var pages = pdfViewer1.Document.Pages;

for (int i = selInfo.StartPage; i <= selInfo.EndPage; i++)
{
	var rects = GetSelectedTextRects(pages[i], i, selInfo);
}


private List<Rectangle> GetSelectedTextRects(PdfPage page, int pageIndex, SelectInfo selInfo)
{
	var ret = new List<Rectangle>();

	if (selInfo.StartPage < 0)
		return ret;

	if (pageIndex >= selInfo.StartPage && pageIndex <= selInfo.EndPage)
	{
		int s = 0;
		if (pageIndex == selInfo.StartPage)
			s = selInfo.StartIndex;

		int len = page.Text.CountChars;
		if (pageIndex == selInfo.EndPage)
			len = (selInfo.EndIndex + 1) - s;

		var ti = page.Text.GetTextInfo(s, len);
		foreach (var rc in ti.Rects)
		{
			var pt1 = pdfViewer1.PageToClient(pageIndex, new PointF(rc.left, rc.top));
			var pt2 = pdfViewer1.PageToClient(pageIndex, new PointF(rc.right, rc.bottom));

			int x = pt1.X < pt2.X ? pt1.X : pt2.X;
			int y = pt1.Y < pt2.Y ? pt1.Y : pt2.Y;
			int w = pt1.X > pt2.X ? pt1.X - pt2.X : pt2.X - pt1.X;
			int h = pt1.Y > pt2.Y ? pt1.Y - pt2.Y : pt2.Y - pt1.Y;

			ret.Add(new Rectangle(x, y, w, h));
		}
	}
	return ret;
}