If you think this makes piracy harder in any way, you are badly mistaken.

It only takes one person to "break" whatever protection there is on the content, its almost entirely irrelevant just how much protection is on that content, because only one person needs to go through the process.

The thing is, by making pdfs harder to get through legit channels they are going to increase traffic through illegitimate channels. It's not about how many files are available, it's about how many people are looking for them.

If someone can't pirate "X in a Nutshell", they'll pirate "Learning X". Either way, nobody is getting their money. No point losing customers over it.