You could use something like this in your AcadDoc.lsp file.
(defun-q mystartup ()
(vl-cmdf "-layout" "set" "layout1")
(vl-cmdf "-Plot" "_Y" "layout1" "DWG to PDF.pc3" "ANSI A (11.00 x 8.50 Inches)" "inches" "landscape" "_No" "Layout" "1:1" "0.00,0.00" "_Yes" "monochrome.ctb" "_Yes" "_No" "_No" "_No" "" "_Yes" "_Yes")
(vl-cmdf "._close" "_No")
)
(setq s::startup (append s::startup mystartup))
Change the appropriate parts as needed.