Do not select any installed Lr templates! Use your own paper size and orientation settings in the Printer Setup.
Then Check the Lr Layout panel- Margins at minimum, Cell size at maximum. (& Page grid 1 row 1 column)
Post screen-clips of Printer setup dialog and the Lr Layout panel, if you are still unsuccessful.
Thanks. I checked these and they were set correctly. I tried a draft print on plain paper and it worked fine. Printed a good one after that and it came out fine too. Not sure but I think closing LR and going back in maybe cleared things up. Anyway, thanks for the info!
I also have this issue. I have not found any reason why LR prints wrong size, because this happens randomly. I feel this is a bug and an annoying one, because LR templates of course should work correctly and I lose many papers because of this. If I define my own custom setup the I get the correct size.
LR developers heads up!