To maintain synchronization, components should be added to a schematic design rather than to a PCB. The schematic design is the master document for the project, and the PCB design is derived from it. When you add a component to the schematic, it is automatically added to the PCB design.
If you are working in a 2D PCB document, you can place components directly on the board. However, footprints with pads should be placed from the linked schematic unless you don't have an associated schematic.