PDFs crashing in iBooks on iPad Pro when the PDFs get too large

All my PDFs read fine and all the functions of Apple iBooks (including text to speech) works just fine during the first hundred pages of a PDF but when it gets over 100 pages Apple iBooks either slows, freezes or crashes. I’ve Reinstalled, I have updated to the current version and this still has happened on multiple iPads, I have not tried it on any window devices. I’m wondering if this is some intentional format governing impedance that Apple has imbedded into iBooks and I have notified apple several times that this needs to be addressed and it’s still does.