For components that have no polarity, like resistors and ceramic capacitors, the pin definition is irrelevant.
For components that do have polarity, like electrolytic capacitors, diodes, ICs, etc., you have to provide polarity information on the silk screen. For instance, draw a line on the silk screen next to the pad corresponding to a line in the component marking (typical in capacitors), use + and/or - symbols, write letters A and K next to the correspondent anode and cathode pins in a diode, etc. For ICs the convention is to mark the location of the pin 1 or A1 in case of a ball grid array. Through-hole ICs or connectors sometimes use a square pad for pin 1 and circular pads for the other pins.
If your board has no silk screen you have to provide polarity information in assembly drawings to clearly define the polarity of components that may present orientation ambiguity.
Based on this information, the production line technicians will properly program the pick-and-place machine to place these components correctly based on the orientation that they come inside the reel.