Well, pH refers to the concentration of protons in water solvent. Since pure sulfuric acid has no water (excluding that which is in equilibrium with sulfur trioxide), pH isn't really well defined for it. A better definition of acidity which does not have this problem is the Hammett acidity function. Sulfuric acid on this scale has an acidity of -12. (Note that this acidity score is not fully comparable to pH. However, with a difference so massive (a factor of one trillion times more acidic), this subtle difference ceases to be relevant.)

If you're asking about corrosivity, sulfuric acid gets its reputation because its also strongly dehydrating. Thus, it does wonderful things like rip the water out of your skin or char paper. I would hazard a guess that the water they've found in the paper does neither of those things.