As sheet sizes and how they're named vary by plotting device I'd import a page setup. I include two for each size. One for plotting and one for creating a PDF of that size.
Code:
^C^C^P(or C:Steal (load "StealV1-8.lsp"))(Steal (strcat (vl-filename-directory (getenv "QnewTemplate")) (chr 92) "AutoCAD Template" (chr 92) "Templates.dwt") (list (list "Page Setups" (list "24×36" "24×36 PDF")))) .regen
I usually create model space drawing first then add whatever size layouts and plot styles I need.
Code:
^C^C^P(or C:Steal (load "StealV1-8.lsp"))(Steal (strcat (vl-filename-directory (getenv "QnewTemplate")) (chr 92) "AutoCAD Template" (chr 92) "Templates.dwt") (list (list "Page Setups" (list "11×17" "11×17 PDF"))(list "Layouts" (list "11×17")))) .regen
Only after knowing what I'm plotting and to what scale do I add dimensions and other annotations.
As I use Lee Mac's Steal from Drawing for importing everything it's already loaded from acaddoc.lsp not in my macros like in the examples above.