SautinSoft.Document может помочь Вашему приложению преобразовать документ из одного формата в
                другой.
 Вам нужно будет только Load() документ и
                Save() в нужном формате:
            DocumentCore dc = DocumentCore.Load("...");
            dc.Save("....");
SautinSoft.Document поддерживает форматы:
| DOCX | RTF | HTML | Текст | Изображения | |
|---|---|---|---|---|---|
| Create/Read/Write | Create/Read/Write | Create/Read/Write | Create/Read/Write | Create/Read/Write | Create/Read(OCR)/Write | 
Полный код
using System.IO;
using SautinSoft.Document;
namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            // Get your free trial key here:   
            // https://sautinsoft.com/start-for-free/
            ConvertFromFile();
            ConvertFromStream();
        }
        /// <summary>
        /// Convert Text to RTF (file to file).
        /// </summary>
		/// <remarks>
        /// Details: https://sautinsoft.com/products/document/help/net/developer-guide/convert-text-to-rtf-in-csharp-vb.php
        /// </remarks>
        static void ConvertFromFile()
        {
            string inpFile = @"..\..\..\example.txt";
            string outFile = @"Result.rtf";
            DocumentCore dc = DocumentCore.Load(inpFile);
            dc.Save(outFile);
			
			// Important for Linux: Install MS Fonts
			// sudo apt install ttf-mscorefonts-installer -y
            // Open the result for demonstration purposes.
            System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo(outFile) { UseShellExecute = true });
        }
        /// <summary>
        /// Convert Text to RTF (file to file).
        /// </summary>
		/// <remarks>
        /// Details: https://sautinsoft.com/products/document/help/net/developer-guide/convert-text-to-rtf-in-csharp-vb.php
        /// </remarks>
        static void ConvertFromStream()
        {
            // We need files only for demonstration purposes.
            // The conversion process will be done completely in memory.
            string inpFile = @"..\..\..\example.txt";
            string outFile = @"ResultStream.rtf";
            byte[] inpData = File.ReadAllBytes(inpFile);
            byte[] outData = null;
            using (MemoryStream msInp = new MemoryStream(inpData))
            {
                // Load a document.
                DocumentCore dc = DocumentCore.Load(msInp, new TxtLoadOptions());
                // Save the document to RTF format.
                using (MemoryStream outMs = new MemoryStream())
                {
                    dc.Save(outMs, new RtfSaveOptions() );
                    outData = outMs.ToArray();                    
                }
                // Show the result for demonstration purposes.
                if (outData != null)
                {
                    File.WriteAllBytes(outFile, outData);
					
					// Important for Linux: Install MS Fonts
					// sudo apt install ttf-mscorefonts-installer -y
                    System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo(outFile) { UseShellExecute = true });
                }
            }
        }
    }
}Imports System.IO
Imports SautinSoft.Document
Namespace Example
	Friend Class Program
		Shared Sub Main(ByVal args() As String)
			ConvertFromFile()
			ConvertFromStream()
		End Sub
                ''' Get your free trial key here:   
                ''' https://sautinsoft.com/start-for-free/
		''' <summary>
		''' Convert Text to RTF (file to file).
		''' </summary>
		''' <remarks>
		''' Details: https://sautinsoft.com/products/document/help/net/developer-guide/convert-text-to-rtf-in-csharp-vb.php
		''' </remarks>
		Private Shared Sub ConvertFromFile()
			Dim inpFile As String = "..\..\..\example.txt"
			Dim outFile As String = "Result.rtf"
			Dim dc As DocumentCore = DocumentCore.Load(inpFile)
			dc.Save(outFile)
			
			' Important for Linux: Install MS Fonts
			' sudo apt install ttf-mscorefonts-installer -y
			' Open the result for demonstration purposes.
			System.Diagnostics.Process.Start(New System.Diagnostics.ProcessStartInfo(outFile) With {.UseShellExecute = True})
		End Sub
		''' <summary>
		''' Convert Text to RTF (file to file).
		''' </summary>
		''' <remarks>
		''' Details: https://sautinsoft.com/products/document/help/net/developer-guide/convert-text-to-rtf-in-csharp-vb.php
		''' </remarks>
		Private Shared Sub ConvertFromStream()
			' We need files only for demonstration purposes.
			' The conversion process will be done completely in memory.
			Dim inpFile As String = "..\..\..\example.txt"
			Dim outFile As String = "ResultStream.rtf"
			Dim inpData() As Byte = File.ReadAllBytes(inpFile)
			Dim outData() As Byte = Nothing
			Using msInp As New MemoryStream(inpData)
				' Load a document.
				Dim dc As DocumentCore = DocumentCore.Load(msInp, New TxtLoadOptions())
				' Save the document to RTF format.
				Using outMs As New MemoryStream()
					dc.Save(outMs, New RtfSaveOptions())
					outData = outMs.ToArray()
				End Using
				' Show the result for demonstration purposes.
				If outData IsNot Nothing Then
					File.WriteAllBytes(outFile, outData)
					System.Diagnostics.Process.Start(New System.Diagnostics.ProcessStartInfo(outFile) With {.UseShellExecute = True})
				End If
			End Using
		End Sub
	End Class
End Namespace
Если вам нужен пример кода или у вас есть вопрос: напишите нам по адресу support@sautinsoft.ru или спросите в онлайн-чате (правый нижний угол этой страницы) или используйте форму ниже: