When you go into EDIT, REPLACE, you should see a button on the bottom
of the Replace window that says MORE. click on More. It gives you
tons of additional options for replacing. You can replace a word with
the same word bolded, underlined etc. you can replace highlighing of
one color with another; a style with another style, single space with
double spaced etc..... it's not just for replace one word with
another. So to replace the word DOG with DOG bolded, type DOG in the
FIND WHAT field, then type DOG again in the REPLACE WITH field. Now
make sure your cursor is blinking in the Replace With field and then
click the MORE button and then on the bottom of that window click on
FORMAT, FONT, choose bold. Then hit your replace all button.
Definitely play around with all the options in the More section of Find
and Replace. It's extremely helpful to know. Hope this helps.