multiple persons comments on the same PDF document at the same time

In my work place, one file is sent out to the team to review and enter their comments.

At the moment, the same file cannot be edited by two persons at the same time. So we both had commented and saved with two different names. In the end, I would add my colleague's comment into the  my version, and consodiate all comments into one and sent to the originator. Once it happened, I missed to consodilate few of my collegue's comments and it was unacceptable as they were important too. Please help if we both can add our comments into the same document. Thanks