Applescript: save all open tabs in Chrome to PDF
I found a work-around, using UI scripting, that does what I need:

tell application "Google Chrome"
    set myWindow to front window
    set myTabs to tabs in myWindow


    set outputFolder to "/Users/nnn/Desktop/PDF/"
    set myCount to 0

    activate

    repeat with myTab in myTabs
        set myCount to myCount + 1
        set fileName to "pdf" &amp; myCount &amp; ".pdf"
        set outputPath to outputFolder &amp; fileName

        --N.B.: the following opens the system print window, not Google Chrome’s
        tell myTab to print

        tell application "System Events"
            tell process "Google Chrome"
                repeat until window "Print" exists
                    delay 0.02
                end repeat

                set printWindow to window "Print"

                tell printWindow
                    set myButton to menu button "PDF"
                    click myButton

                    repeat until exists menu 1 of myButton
                        delay 0.02
                    end repeat

                    set myMenu to menu 1 of myButton
                    set myMenuItem to menu item "Save as PDF" of myMenu
                    click myMenuItem

                    repeat until exists sheet 1
                        delay 0.02
                    end repeat

                    set saveSheet to sheet 1
                    tell saveSheet
                        set value of first text field to fileName
                        keystroke "g" using {command down, shift down}

                        repeat until exists sheet 1 of saveSheet
                            delay 0.02
                        end repeat

                        set goDialogue to sheet 1 of saveSheet

                        tell goDialogue
                            set value of first combo box to outputFolder
                            click button "Go"
                        end tell

                        click button "Save"
                    end tell
                end tell

                repeat while printWindow exists
                    delay 0.02
                end repeat
            end tell
        end tell
    end repeat
end tell