PM> Install-Package Spire.Doc

using Spire.Doc;
using Spire.Doc.Documents;
using Spire.Doc.Fields;

namespace InsertOleObjects
{
    internal class Program
    {
        static void Main(string[] args)
        {
            // Create an instance of the Document class
            Document doc = new Document();
            // Load a Word document
            doc.LoadFromFile("Example.docx");

            // Get the first section
            Section section = doc.Sections[0];

            // Add a paragraph to the section
            Paragraph para1 = section.AddParagraph();
            para1.AppendText("Excel File: ");
            // Load an image that will be used as the icon of the OLE object
            DocPicture picture1 = new DocPicture(doc);
            picture1.LoadImage("Excel-Icon.png");
            picture1.Width = 50;
            picture1.Height = 50;
            // Append an Excel spreadsheet to the paragraph as an OLE object
            para1.AppendOleObject("Budget.xlsx", picture1, OleObjectType.ExcelWorksheet);

            // Add a paragraph to the section
            Paragraph para2 = section.AddParagraph();
            para2.AppendText("PDF File: ");
            // Load an image that will be used as the icon of the OLE object
            DocPicture picture2 = new DocPicture(doc);
            picture2.LoadImage("PDF-Icon.png");
            picture2.Width = 50;
            picture2.Height = 50;
            // Append a PDF file to the paragraph as an OLE object
            para2.AppendOleObject("Report.pdf", picture2, OleObjectType.AdobeAcrobatDocument);

            // Add a paragraph to the section
            Paragraph para3 = section.AddParagraph();
            para3.AppendText("PPT File: ");
            // Load an image that will be used as the icon of the OLE object
            DocPicture picture3 = new DocPicture(doc);
            picture3.LoadImage("PPT-Icon.png");
            picture3.Width = 50;
            picture3.Height = 50;
            // Append a PowerPoint presentation to the paragraph as an OLE object
            para3.AppendOleObject("Plan.pptx", picture3, OleObjectType.PowerPointPresentation);

            // Add a paragraph to the section
            Paragraph para4 = section.AddParagraph();
            para4.AppendText("Word File: ");
            // Load an image that will be used as the icon of the OLE object
            DocPicture picture4 = new DocPicture(doc);
            picture4.LoadImage("Word-Icon.png");
            picture4.Width = 50;
            picture4.Height = 50;
            // Append a Word document to the paragraph as an OLE object
            para4.AppendOleObject("Introduction.docx", picture4, OleObjectType.WordDocument);

            doc.SaveToFile("InsertOLE.docx", FileFormat.Docx2013);
            doc.Close();
        }
    }
}

using Spire.Doc;
using Spire.Doc.Documents;
using Spire.Doc.Fields;
using System;

namespace InsertOrExtractOleObjects
{
    internal class Program
    {
        static void Main(string[] args)
        {
            // Create an instance of the Document class
            Document doc = new Document();
            // Load a Word document
            doc.LoadFromFile("InsertOLE.docx");

            int i = 1;
            // Iterate through all sections of the Word document
            foreach (Section sec in doc.Sections)
            {
                // Iterate through all child objects in the body of each section
                foreach (DocumentObject obj in sec.Body.ChildObjects)
                {
                    // Check if the child object is a paragraph
                    if (obj is Paragraph par)
                    {
                        // Iterate through the child objects in the paragraph
                        foreach (DocumentObject o in par.ChildObjects)
                        {
                            // Check if the child object is an OLE object
                            if (o is DocOleObject ole)
                            {
                                string s = ole.ObjectType;
                                string ext = "";

                                // Check if the OLE object is a PDF file
                                if (s.StartsWith("AcroExch.Document"))
                                {
                                    ext = ".pdf";
                                }
                                // Check if the OLE object is an Excel spreadsheet
                                else if (s.StartsWith("Excel.Sheet"))
                                {
                                    ext = ".xlsx";
                                }
                                // Check if the OLE object is a PowerPoint presentation
                                else if (s.StartsWith("PowerPoint.Show"))
                                {
                                    ext = ".pptx";
                                }
                                // Check if the OLE object is a Word document
                                else if (s.StartsWith("Word.Document"))
                                {
                                    ext = ".docx";
                                }
                                else
                                {
                                    continue;
                                }

                                // Write the data of OLE into a file in its native format
                                using (var file = System.IO.File.OpenWrite($"Output/OLE{i}{ext}"))
                                {
                                    file.Write(ole.NativeData, 0, ole.NativeData.Length);
                                }

                                i++;
                            }
                        }
                    }
                }
            }

            doc.Close();
        }
    }
}