Replication for a store network

I need to set up a replication system for our stores: there is the main SQL Server to our headquarter and local MS SQL Express servers on each premise, serving the local POS software.
We need to consolidate all the data on the main server and thus have the data accesible.
Some documents concerning product transfer in between stores or with the main warehouse need to be transferred to the local servers.
I have never used Replication but I hope this mechanism can help us with this scenario.
Can you please help me with some good practices on how to organize the replication and all other information you think it is necessary.

I can't figure out how replication treats Identity columns (most of them being used in the Primary Keys)
Many data models come in pair tables: Header (one record per document) and Lines, paired with the header by means of an DocumentId identity in Header. Since DocumentId is generated on local SQL Servers and must be unique, replication should change that value to keep it unique but that will break Header-Lines pairing.....

Thank you,