Also, you can manufacture fraudulent ballots, but common sense says that A) none of those fraudulent ballots would be cast, B) they would be destroyed (a ballot is paper. You can destroy paper), or C) they would count as invalid ballots 
Fraudulent ballots are not fake ballots - they are real ballots (most commonly overprinted and over distributed mail-ins) fraudulently cast by political operatives in the names of actual registered voters (some alive, some dead) who did not bother to show up at the polls. These political operatives see no problem with this, believing that their ballots reflect how such unmotivated voters would have voted had they taken the trouble to get off the couch and show up.
Unfortunately, once the mail-in envelopes are discarded, there is no way to trace the true origins of these ballots.
That's how so many districts in cities like Philadelphia and Houston end up with 115% voter turnouts - which you are never allowed to question or you must be some kind of racist. 