Word.Range r = WordDoc.Range(ref onewstart, ref onewe);
find = r.Find;
find.Text = "Rest";
r.Find.Font.Underline = Word.WdUnderline.wdUnderlineSingle;
r.Find.Font.Bold = 1;
find.Execute(ref oMissing, ref matchword, ref matchwholeword, ref matchwildcards, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing);
if (find.Found)
{
Word.Table oTable;
Word.Range newrng;
int i = r.Start;
object o = r.Start;
object e = r.End;
newrng = WordDoc.Range(ref o, ref e);
string te = newrng.Text;
oTable = WordDoc.Tables.Add(newrng, 1, 1, ref oMissing, ref oMissing);
oTable.Columns.Item(1).Cells.Item(1).Range.Text = te;
oTable.Rows.Item(1).Range.Bold = 1;
oTable.Borders.OutsideLineStyle = Word.WdLineStyle.wdLineStyleNone;
oTable.Cell(1, 1).Shading.BackgroundPatternColor = Word.WdColor.wdColorGray10;
object os = oTable.Range.End;
object oe = oTable.Range.End + 1;
WordDoc.Range(ref os, ref oe).Font.Size = 2;
}
like this u can able to change the FOnt Style of Word