Elsewhere in this discussion, I suggested the same thing, except using envelopes instead of folding. You also need to separately tally the other N-1 discarded ballots to make sure they're not being brought out of the polling station. (Discarded ballots brought out of the polling station prove to jackbooted thugs that you didn't vote for the opposition.)
Though, I don't understand the purpose of the pen in the proposal. There's already one of every possible ballot, so you don't use the pen to mark candidates. You don't write your name on the ballot, as that would ruin anonymity. You don't cross-out the ballots that you don't cast, as that would open back up the weakness to photography. So, how is the pen used?
Also, what's the purpose of having the official put the ballot in the box instead of having the voter put the ballot in the box? Is it to prevent multiple votes from being cast? You need to have a discard box for the unused ballots and tally those discarded ballots in order to detect when the jackbooted thugs force people to walk out of the polls with their discarded ballots in order to prove how they didn't vote. Once you have this, you've also got multi-vote detection.
Though, I don't understand the purpose of the pen in the proposal. There's already one of every possible ballot, so you don't use the pen to mark candidates. You don't write your name on the ballot, as that would ruin anonymity. You don't cross-out the ballots that you don't cast, as that would open back up the weakness to photography. So, how is the pen used?
Also, what's the purpose of having the official put the ballot in the box instead of having the voter put the ballot in the box? Is it to prevent multiple votes from being cast? You need to have a discard box for the unused ballots and tally those discarded ballots in order to detect when the jackbooted thugs force people to walk out of the polls with their discarded ballots in order to prove how they didn't vote. Once you have this, you've also got multi-vote detection.