You can use the following method to convert PDF pages to images:

public async static void RenderPDFPagesAsync(String pdf)
        {

            StorageFolder tempFolder = ApplicationData.Current.LocalFolder;
            StorageFile file = await tempFolder.GetFileAsync(pdf);

            PDFDoc doc = new PDFDoc();
            try
            {
                using (var stream = await file.OpenReadAsync())
                {
                    if (doc.Open(stream, "") == PDF_ERROR.err_ok)
                    {
                        double previousPageHeight = 0, previousPageWidth = 0;
                        PDFBmp m_dib = null;

                        foreach (var index in Enumerable.Range(0, (int)doc.PageCount))
                        {
                            PDFPage page = doc.GetPage(index);
                            try
                            {
                                var cFileName = index.ToString() + ".jpg";

                                page.RenderPrepare();

                                var pageHeight = doc.GetPageHeight(index);
                                var pageWidth = doc.GetPageWidth(index);
                                float scale = (float)1.0;                             
                                pageHeight = pageHeight * scale;
                                pageWidth = pageWidth * scale;


                                if (previousPageHeight != pageHeight || previousPageWidth != pageWidth || m_dib == null)
                                {
                                    m_dib = new PDFBmp((int)pageWidth, (int)pageHeight);
                                    previousPageHeight = pageHeight;
                                    previousPageWidth = pageWidth;
                                }

                                m_dib.Reset(0xFFFFFF);
                                PDFMatrix mat = new PDFMatrix(scale, -scale, 0, pageHeight);
                                page.RenderToBmp(m_dib, mat, true, PDF_RENDER_MODE.mode_normal);
                                m_dib.SaveJPG(tempFolder.Path + "\\" + cFileName, 90);
                            }
                            catch (Exception e) { } 
                            finally
                            {
                                page.Close();
                            }
                        }
                    }
                }
                doc.Close();
            }
            catch (Exception ex) { }
        }