iBooks won't open in version 9.2.1

Perhaps, the PDFs file is corrupt and that's what is causing the problem.

I assume that iBooks opens for a brief second and then crashes back to the home screen. It that is not what happens, please clarify. If that is what happens, first try closing the app completely and then force restart the iPad.

Press the Home button two times quickly. You'll see small previews of your recently used apps. Swipe left to find the app you want to close. Swipe up on the app's preview to close it

To force restart your device, press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.

If that failed to fix it, remove the pdf that you added via iTunes. You will have to go through iTunes again and unsync the pdf file. Then go through the steps again of closing iBoooks on the iPad and force restart.

If that fixes iBooks, you have to fix the pdf file before you try to add it back to the device.

You might want to consider resetting all settings. Resetting all settings to factory default might remove a corrupt setting that is causing the problem. Settings>General>Reset>Reset All Settings. No data is lost when you do this, but all device settings have to be entered again, including your WiFi network passwords. The iPad will reboot on its own when you reset the settings.

I Have reset all settings several times in the past and never lost anything. It does take a little time getting all of your device's settings back to where you had them, but it might help.

You're welcome. I'm happy to hear that the app is working again.