I'm running Lightroom 2015.9 on Mac Sierra. When I change paper sizes in Lightroom, the paper size doesn't change properly at the printer and the image comes out wrong. This problem doesn't happen in Photoshop or other programs, just Lightroom. I'm printing to an Epson P800. I had a similar issue with my Epson 9800 so it's not the printer. I've been printing digitally since the 90's and am well familiar with the various Page Setup settings. The only thing that seems to work is restarting the computer. Has anyone had a similar issue?
The image below should have printed at full size on 8.5x11.
This image should have printed full page at 13x19.
Thanks to all who respond, John
I'd be interested in seeing screenshots of your printer driver page setup, the Layout panel, and the main preview window with the information overlay (I) or the rulers on.
I am having the same problem in LR CC and what is now called Classic. Its random too. Sometimes I can play with ordination and it somehow works. But I can come back the next day and it will do exactly what yours is doing. Did you ever find the problem?