Simaultenous Collaboration for Filling a .pdf Form

As the title indicates, I need to be able to collaborate in real-time regarding filling out a 50 page .pdf form. 

This is not needed for adding comments, it is needed for at least two people to be able to simultaneously collaborate on a .pdf form in real-time.

What would be the best route to take with this endeavor?

Any input would be much appreciated.

Thanks.