Ariculate Storyline won't let me add a PDF into Resources Tab

Hello E-Learning Heroes community,

I begin to come across a problem. I made exported a PDF from Indesign and I tried to put it into a RESOURCES tab in Storyline but it gives Articulate Storyline Error Report popup for no reason. I updated the the application and it still gives me an issue. I tried turning off my computer and turning it back on. The problem still persists.

I tried with another PDF and for some reason it works! But not this PDF. 

Anyone with InDesign and Articulate could tell me what the issue is?? This doesn't make any sense to me.