If you abandoned the quest and lost pages, you will need to restart the quest and earn the pages again.
Can't complete Victory in the Depths quest
What to do if you were unable to complete the quest Stepping Through the Darkness in a Horrific Vision.
What to do if the quest doesn't activate or constantly resets
Information about how to queue for MoP raids in LFR
The page requirements for these quests were reduced, but you may not see that reflected ingame. You will still be able to complete the quests.
Player unaware how unlocking Adventure Mode works
It is not possible to change the raid size in strict instance-based lockout raids
An explanation of why you are "locked out" from a raid boss when you find it missing or already dead.