word转图片使用的Aspose组件，Aspose.word.dll 

 public bool Word2Png(string docFile, string pngDir, out int pngCount)
        {
            ImageSaveOptions options = new ImageSaveOptions(SaveFormat.Png);
            options.Resolution = 300;
            options.PrettyFormat = true;
            options.UseAntiAliasing = true;

            pngCount = 0;
            try
            {
                Aspose.Words.Document doc = new Aspose.Words.Document(docFile);
                for (int i = 0; i < doc.PageCount; i++)
                {
                    options.PageIndex = i;
                    doc.Save(pngDir + i + ".png", options);

                    pngCount++;
                }
                return true;
            }
            catch
            {
                return false;
            }
        }

PDF 转图片使用的是Aspose.pdf.dll 组件

 public bool PDF2PNG(string srcPdfPath, string desPicPath)
        {
            try
            {
                Aspose.Pdf.Document pdf = new Aspose.Pdf.Document(srcPdfPath);
                for (int pageCount = 1; pageCount <= pdf.Pages.Count; pageCount++)
                {
                    using (FileStream p_w_picpathStream = new FileStream(desPicPath + "\\" + pageCount + ".png", FileMode.Create))
                    {
                        //create Resolution object
                        Aspose.Pdf.Devices.Resolution resolution = new Aspose.Pdf.Devices.Resolution(300);
                        Aspose.Pdf.Devices.PngDevice pngDevice = new Aspose.Pdf.Devices.PngDevice(resolution);

                        //convert a particular page and save the p_w_picpath to stream
                        pngDevice.Process(pdf.Pages[pageCount], p_w_picpathStream);
                        //close stream
                        p_w_picpathStream.Close();
                    }
                }
                return true;
            }
            catch (Exception e)
            {
                return false;

            }
        }