Synonyms for Fill out:

n.

caption, grow, enshrine, annotate, enter, date, backdate, address. sweat off, sign, stay off, fat camp, answer, trim down, put on, slim down, apply, lose. fill out (noun)
pad, flesh out, plump out, round, round out, fatten up, fatten out, complete, fatten, make out, plump, fat, eke out.

v.

change (verb)
round out.
communication (verb)
make out, complete.
enlarge (verb)
round out, grow.
insert (verb)
answer, make out, sign, complete.

Other synonyms:

enshrine, caption, annotate, fat camp, date, grow. slim down, backdate, trim down, sweat off, enter. stay off. address. lose. put on. Other relevant words:
answer, grow, sign, enter.