I can't see what other people has done

I have a big issue right now. I have a document shared in google drive with a friend and we both have to make annotations in the same document. I first edited the first page and my friend could see it, so I started editing the next pages (2,3,…) and my friend edited a few pages later (for example: 12, 13,…). But my friend can’t see what I have done (except page 1) and I can’t see what she has done. The document has +50 pages.
So, if we don’t see what the other has done, we can’t do the proyect. We need to solve this as soon as possible.

Hi, I’ve finally found a solution. My friend didn’t have MetaPDF’s program connected with google drive, directly from google drive. She entered to metaPDF and then loging wth her account.

I hope this can help someone in the future.

PD: sorry for my english, I’m Spanish.