private void btnAddToAutoCorrect_Click(object sender, EventArgs e)
        {
            string FONT = "Arial";
            Word.Application app = new Word.Application();
            Object fileName = @"D:\тест.docx";
            Object missing = Type.Missing;
            app.Documents.Open(ref fileName);
            Word.Find find = app.Selection.Find;
           
            find.Text = "2";
            find.Replacement.Text = "3333";

            if (find.Font.Name == FONT)
            {
                Object wrap = Word.WdFindWrap.wdFindContinue;
                Object replace = Word.WdReplace.wdReplaceAll;
                find.Execute(FindText: Type.Missing,
                MatchCase: false,
                MatchWholeWord: false,
                MatchWildcards: false,
                MatchSoundsLike: missing,
                MatchAllWordForms: false,
                Forward: true,
                Wrap: wrap,
                Format: false,
                ReplaceWith: missing, Replace: replace);
            }
            app.ActiveDocument.Save();
            app.ActiveDocument.Close();
            app.Quit(); 
        }

Word.Application app = new Word.Application();
            Object fileName = @"D:\тест.docx";
            Object missing = Type.Missing;
            app.Documents.Open(ref fileName);
            Word.Find find = app.Selection.Find;
           
            find.Text = "2";
            find.Replacement.Text = "3333";
                Object wrap = Word.WdFindWrap.wdFindContinue;
                Object replace = Word.WdReplace.wdReplaceAll;
                find.Execute(FindText: Type.Missing,
                MatchCase: false,
                MatchWholeWord: false,
                MatchWildcards: false,
                MatchSoundsLike: missing,
                MatchAllWordForms: false,
                Forward: true,
                Wrap: wrap,
                Format: false,
                ReplaceWith: missing, Replace: replace);
            app.ActiveDocument.Save();
            app.ActiveDocument.Close();
            app.Quit();