How can users have confidence that there are no backdoors in paper wallet generators? I'm thinking of issues like the randomization not being truly random. I appreciate that some users could examine the code themselves, but what assurances do less technically skilled users have?
There's really no way for a nontechnical user to know. In fact, most technical users do not have the specific technical knowledge required to evaluate cryptographic code (including the random number generator). Therefore, it comes down to a matter of trust. If the user does not directly trust the software author, they may sufficiently trust somebody else who has evaluated the technical aspects of the software.