Comment and highlighting problem

Hi. I am experiencing a problem some time now that i m not able to solve. I am reading a book pdf and i m highlighting and commenting on this pdf. But now the adobe program crashes when i open this pdf, meaning that is really slow when running or not being able to read the comments i ve made. Keeping in mind that this is 3 years work is really frustrating... I have a high end system so i dont think its crashing due to system being inadequate to run the programm. Thank you!