They are NOT paperless. When the machine is turned on in preparation for voting, it first prints out a zero proof slip, similar to a cash register tape, that shows any votes in the machine. If it shows anything other than zero the machine is not to be used and you call the county for a reset. All four election judges have to sign the slip, 2 Rs and 2 Ds.
After the polls close it prints out four copies of the results, one to be posted at the polling place and three turned in with any provisional ballots cast, again all signed by the board workers.
The total tally of voters on the machine's running tabulation is supposed to match the number who have signed in to vote. The results are turned in to the municipal clerk's office.
All in all, it's pretty secure.
And that's why the RATs are so big on mail-ins.