Word replacer for Word Document (C#)

DocReplacer.cs

using System;
using System.Text.RegularExpressions;

namespace ConsoleApp1
{
    class Doc_Replacer
    {
        static void Main(string[] args)
        {

            // Import word document and convert into string.
            string wordDoc =
@"We like working here at Leadsoft IT. 
We are not limited here at Leadsoft It Limited.";

            Replacer(wordDoc);

        }

        static string Replacer(string wordDoc)
        {

            string replaceWith = "Leadsoft IT Limited";
            string pattern = "(Leadsoft IT(?!.*Limited))";

            string print_str = Regex.Replace(wordDoc, pattern, replaceWith
                , RegexOptions.IgnoreCase);

            // Console.WriteLine(print_str);
            return print_str;
        }
    }
}