How do I get Automator actions for Microsoft Powerpoint and Word?
Microsoft Office for Mac 2011 (and 2008) includes several Automator workflows, but Microsoft is no longer providing Automator actions for Office 2016.

So, you must run an AppleScript from the Automator workflow

Here is the script (edited):

on run {input, parameters}
    set theOutput to {}
    tell application "Microsoft PowerPoint" -- work on version 15.15 or newer
        launch
        set theDial to start up dialog
        set start up dialog to false
        repeat with i in input
            open i
            set pdfPath to my makeNewPath(i)
            save active presentation in pdfPath as save as PDF -- save in same folder
            close active presentation saving no
            set end of theOutput to pdfPath as alias
        end repeat
        set start up dialog to theDial
    end tell
    return theOutput
end run

on makeNewPath(f)
    set t to f as string
    if t ends with ".pptx" then
        return (text 1 thru -5 of t) &amp; "pdf"
    else
        return t &amp; ".pdf"
    end if
end makeNewPath


This script return path of the PDF files to the next action.



Here is the workflow: