It seems like sources was way to set watched folders in 7.2.x.
Now when you click on "sources" it takes you to Service management.
In "Name" type "generate", and say filter. It should fetch you GeneratePDFService1:0.
Click on the link, and choose "End Points" tab, which will allow you to set "watched folder" for this service. (Select "watched folder" in the dropdown and say add).