AFAIK Apple no longer provides a specific user guide for the original wired EarPods on their website.
However, the following should be the basic controls:
- Play/Pause: Press the center button once.
- Skip to the next track: Double-press the center button.
- Go back to the previous track: Triple-press the center button.
- Fast-forward: Double-press the center button and hold on the second press.
- Rewind: Triple-press the center button and hold on the third press.
- Answer/End a call: Press the center button once.
- Decline an incoming call: Press and hold the center button for about two seconds, then release. Two beeps will confirm the call was declined.
- Switch between calls: If you’re on a call and another one comes in, press the center button once to switch to the new call and put the current call on hold. Press again to switch back.