@rngoes,
To embed reports you need to be able to call REST API/SDK which is a part of Power BI Pro license (see the difference between Free and Pro here - https://docs.microsoft.com/en-us/power-bi/service-free-vs-pro). This is a minimum requirement.
But there will be a limitation of how much embed tokens you can generate at the same time. Usually, it is pretty enough even for production solution. Unfortunately, it is not documented but I think it is about 250.
To remove this limit you can buy additional dedicated capacity called Premium. There are actually two similar types of it - Azure Power BI Embedded and MS Office 365 Power BI Premium. Both allow you to embed an unlimited number of reports. Here are a lot of an official documentation related to that - https://docs.microsoft.com/en-us/power-bi/whitepapers. But anyway it is not required to use it. You can stay just with Pro.
Additionally, here is an instruction on how to embed - https://docs.microsoft.com/en-us/power-bi/developer/integrate-report
and sample from Microsoft - https://microsoft.github.io/PowerBI-JavaScript/demo/v2-demo/index.html
