public void RenderPage()
{
    //Initialize the SDK library
    //You have to call this function before you can call any PDF processing functions.
    PdfCommon.Initialize();

    //Open and load a PDF document from a file.
    using (var doc = PdfDocument.Load(@"c:\test001.pdf"))
    {
        int i = 0;
        //Iterate all pages;
        foreach (var page in doc.Pages)
        {
            //Gets page width and height measured in points. One point is 1/72 inch (around 0.3528 mm)
            int width = (int)page.Width;
            int height = (int)page.Height;

            //Create a bitmap
            using (var bmp = new PdfBitmap(width, height, true))
            {
                //Fill background
                bmp.FillRect(0, 0, width, height, Color.White);
                //Render contents in a page to a drawing surface specified by a coordinate pair, a width, and a height.
                page.Render(bmp, 0, 0, width, height,
                    Patagames.Pdf.Enums.PageRotate.Normal,
                    Patagames.Pdf.Enums.RenderFlags.FPDF_LCD_TEXT);
                //Get .Net image and save it into file
                bmp.Image.Save(string.Format(@"c:\test001_pdf_page_{0}.png", i++), ImageFormat.Png);
            }
        }
    }

}

PdfCommon.Initialize();
var ocr = OcrApi.Create();
ocr.Init(Languages.English);

double scaleFactor = 3;

using (var doc = PdfDocument.Load(@"d:\1\1.pdf"))
{
	foreach(var page in doc.Pages)
	{
		int width = (int)(page.Width * scaleFactor);
		int height = (int)(page.Height * scaleFactor);
		using (var bitmap = new PdfBitmap(width, height, true))
		{
			//Fill background
			bmp.FillRect(0, 0, width, height, Color.White);
			//Render page into image
			page.Render(bitmap, 0, 0, width, height, PageRotate.Normal,  RenderFlags.FPDF_LCD_TEXT);
			//OCR image
			string text = ocr.GetTextFromImage(bitmap.Image as Bitmap);
		}
	}
}