Is there any limitation on the size of the migrated documents in migration-center?

migration-center itself does not limit the size of any content file it processes. However, the target enterprise content management (ECM) system of a migration, the operating system (OS) of the computer where you install the migration-center job server, or the network file share used to store the content files may impose such a limit. Please check the relevant ECM and OS system documentation when planning your migration.