It is not practical at all not to do PDF. Also hard copies can be copied and shared.
It is not acceptable from NFPA to limit themselves to Hard books only.
If is about copyright, there is alot of ways to protect the PDF.
@TravisMack
The issue is not to have the books for free.
What's strange that NFPA is not providing pdf at all. You have to buy the hard copies book (~4000 pages).
How can you search it ??
On the other hand, rest assured and don't worry about NFPA.
They are making alot of money from trainings...