Hi @Anonymous,

I go back that far with AutoCAD too but I wasn't published!

So, I made a quick Screencast video from my AutoCAD 2017.2.

I select PageSetup without even selecting a printer and can go to Manage Custom Sizes.  If this is not an option for you, try installing a large format printer such as the HP Pagewide (select a dummy IP address to get it to install). Please also go to a layout tab (I know you said you haven't really worked that way yet) and see if you have additional options for the paper sizes in the page setup.

Let me know if this helps.