Microsoft does a great job warning users that Replication Design Masters will be significantly larger in size than MDB files not in a Replication set. What is not underscored (at runtime) is the fact that the Tools > Replication > Synchronize Now... command will cause all MDBs involved in synchronization to grow in size as well.

Compating the database helps but does not reduce the size of the database file to the size it was before replication. Here is a real-world example: to synchronize a change in one record in a Replica set all MDBs grow over ~100KBs! Running the compact command after synchonization may shave up to ~50KB off this size increase. I can only assume that this growth in file size is due to data being written to the hidden tables created by Replication.