Transactional Replication uses 3 agents: snapshot, log reader, and distribution.
snapshot and log reader run at Distributor. Snapshot agent accesses the publisher to create a copy of publication and put it in Default Snapshot Folder. Log Reader Agent accesses the publisher for the logs and put them into the Distributor database.
Distribution Agent accesses the Distributor for the logs. The security of distribution agent must be in PAL and a login in SQL server instance of Distributor database.
Make sure that the Default Snapshot Folder of publisher uses UNC (\\server\data) path.
