edit a macro on the character you want to receive macros in, change macro books.
go to FFXI/USER/????, use windows search and type in `modified:today' and press enter, find which one was last modified, note the folder name it's in
do the same thing on the character you want to copy macros from
close the instance for the character you want to receive macros in
delete every file starting with mcr from receiving char's folder
copy every file starting with mcr from sending char's folder to receiving char's folder
log back in
if you want to get more specific:
mcr.ttl is macro book 1-20 titles
mcr_2.ttl is macro book 21-40 titles
mcr.dat mcr1.dat .. mcr.9.dat are macro book 1's contents
mcr10.dat mcr11.dat .. mcr19.dat are macro book 2's contents
mcr20.dat mcr21.dat .. mcr29.dat are macro book 3's contents
(one file per set of 20 macros, all the way up to mcr399.dat for book 40 set#10)