Following your example does not seems to right.
I have added the following code to add image to the page
Paragraph paragraph = new Paragraph(document);
paragraph.AppendText("This is an image.");
//Insert an image.
paragraph.AppendPicture(Image.FromFile("image.jpg"));
seems to be names space confliction please let me know the names space for the Image.FromFile I am currently using following spaces
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Collections;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;
using smp_class.Partbuilderbuild;
using smp_class.Quote;
using smp_class.Redirect;
using System.Data.SqlClient;
using Spire.Doc;
using Spire.Doc.Interface;
using Spire.Doc.Documents;
using Spire.Doc.Utilities;
using Spire.Doc.Collections;
Thank you.