You can manage two way documents synchronization.
Block "Bitrix24" provides settings from "Bitrix24" to "Kladana" synchronization.
Block "Kladana" provides settings from "Kladana" to "Bitrix24" synchronization.
You can use both blocks or only one. For example, you can use one-way synchronization from "Bitrix24" to "Kladana" for invoices and one-way synchronization from "Kladana" to "Bitrix24" for customer orders.

The invoice numbering is kept default.