I randomly stumbled upon this and got slightly worried because anything game breaking...concerns me. This is from the wiki in regards to the scroll.

WARNING: Acquisition of this item BEFORE completion of Skyrim main questline (defeating Alduin) or completion of the Markarth Quest http://elderscrolls.wikia.com/wiki/The_Forsworn_Conspiracy , will cause the Dragon Scroll to disappear permanently. This will kill ALL of the players chances at completing the main storyline. If youre doing the quest Discerning the Transmundane and are after the Oghma Infinium, either ensure the above mentioned Quests are completed, or you will be unable to complete the Dawnguard Questline as well

Is that someone joking? Or am I missing something...you HAVE to get it before the main questline?

I now have it in my inventory and have already read it at the time tear but I can't drop it. Other than Dawnguard why doesn't it let me drop it, basically pre Dawnguard could I store it? I have completed the Forsworn Conspiracy a long time ago and I am at the section of Discerning the Transmundane where I need to acquire blood. Is that saying if I complete the Transmunade quest I will lose the Dragon Scroll? So confused by that...but I have played too many hours to not look into things like this. Sorry