We have created 36x42 sheet under the "Manage custom sizes" and published to PDF out of AutoCAD LT. Open in Adobe Reader and go to print to our Ricoh 5100 wide format laser printer, we get the prints, almost to scale, but they are off a little. Almost like it is fitting to page.
Settings are set to be actual size when printing. It only happens on the custom sheet sizes created.
AutoCAD LT 2014
Mac OSx 10.10.1
Adobe Reader 11.0.10