Alfresco Community Edition can be used with any number of employees. The software does not have any technical / licensing limits. With regards to scalability, it is foremost a question of how these employees will use Alfresco, how reliable the access needs to be, and what kind of server infrastructure is being used to run Alfresco. There are no inherent, critical advantages in using Enterprise Edition over Community Edition, as both share 99.x% of their code base. The primary difference may be clustering (Enterprise-only), but this isn't necessary to support larger user bases provided a decent infrastructure and/or use case scoping.
