I am planning to use raspberry pi in an embedded design. Is there any way i can prevent the pi from automatically turning on when plugged in?
If you have a Rev 2 Raspberry Pi you should have a P6 header, which is intended for a reset switch.
I would imagine if you held the board in reset from before powering up (the pins shorted) it should prevent it from booting up until you release it from reset (disconnect the pins).
This will require a small amount of electronics, I assume this is not a problem if it is for an embedded application.
keeping that pin shorted is a bad idea for the Pi and the power supply(it puts a load on it causing heat).
you need to build a software switch for power on if your intent is to use it with other devices that would turn it on (done by a relay to control power to the main port) or hard wire a actual switch for the power.