You need to cerate:
- custom paper size for the Layouts you have in the drawing - 916.8 x 640 mm for the first Layout in the drawing and 700 x 700 mm for the second Layout.
- named Page Setup with your current System printer (plotter) for each of the Layouts ans use custom paper sizes you created earlier for each Layout.
To create named Page Setup which you can use on your Mac you need to use Page Setup Manager from File menu.
In Page Setup Manager dialog you click on "+" button, give it the name, select page setup to start from, clicking on Continue. In your drawing you will get an alert from AutoCAD -"HP Designjet T610 44in HPGL2.pc3: The printer in this configuration cannot be found. The default printer in the system will be used." - just ignore it and proceed.
In Page Setup Manager assign custom Paper size to the Layout and make other adjustments here - plot style table, what to print, etc. If you never used this dialog you need to expand it with small round button on the bottom right - you will see all additional settings.
After you pick on OK, page setup is ready for use. Select its name in the list of page setups in Page Setup Manager window, than use "gear" menu to set page setup you created as current for the Layout.
Repeat the step for each Layout you want to print.
Maxim