I want to convert a word file into PDF format without using Microsoft interop library?

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protected void Button1_Click(object sender, EventArgs e)
    {
        if (FileUpload1.HasFile)
        {
            string extention = Path.GetExtension(FileUpload1.PostedFile.FileName);
            if (extention.ToLower() == ".doc" || extention.ToLower() == ".docx")
            {
                string path = System.IO.Path.GetFullPath(FileUpload1.PostedFile.FileName);
                string filename = TextBox1.Text;
                FileUpload1.SaveAs(Server.MapPath("pdf\\") + filename);
                ConvertTopdf(path, filename);
                Label1.Text = "File upload Successfull";
            }
            else
            {
                Label1.Text = "Please Select the word file only";
            }
        }
        else
        {
            Label1.Text = "Please Selet the File";
        }
    }
    public void ConvertTopdf(string path, string filename)
    {
        SautinSoft.UseOffice u = new SautinSoft.UseOffice();
        if (u.InitWord() == 0)
        {
            //convert Word (RTF, DOC, DOCX to PDF)
            u.ConvertFile(path, Server.MapPath("pdf\\") + filename, SautinSoft.UseOffice.eDirection.DOC_to_PDF);
        }
        u.CloseOffice();
    }

What I have tried:

protected void Button1_Click(object sender, EventArgs e)
{
if (FileUpload1.HasFile)
{
string extention = Path.GetExtension(FileUpload1.PostedFile.FileName);
if (extention.ToLower() == ".doc" || extention.ToLower() == ".docx")
{
string path = System.IO.Path.GetFullPath(FileUpload1.PostedFile.FileName);
string filename = TextBox1.Text;
FileUpload1.SaveAs(Server.MapPath("pdf\\") + filename);
ConvertTopdf(path, filename);
Label1.Text = "File upload Successfull";
}
else
{
Label1.Text = "Please Select the word file only";
}
}
else
{
Label1.Text = "Please Selet the File";
}
}
public void ConvertTopdf(string path, string filename)
{
SautinSoft.UseOffice u = new SautinSoft.UseOffice();
if (u.InitWord() == 0)
{
//convert Word (RTF, DOC, DOCX to PDF)
u.ConvertFile(path, Server.MapPath("pdf\\") + filename, SautinSoft.UseOffice.eDirection.DOC_to_PDF);
}
u.CloseOffice();
}