Plot settings for each layout tab can be found using:
(dictsearch (namedobjdict) "ACAD_LAYOUT")
then performing entgets on the data returned.
(Use 350 and 3 assoc values)...
eg. (setq tmp (entget (cdr (nth 11 (dictsearch (namedobjdict) "ACAD_LAYOUT")))))
Check under PLOTSETTINGS in the help file for assoc values for X,Y page size coordinates.
Don't forget about the minimum X and Y values as well
