i tried a code that i found elsewhere but it's not working
exiftool.exe -d %Y '-fileName${Title} - $Author [$CreateDate]'.pdf -ext pdf
You didn't include the tag copy operation. Try
exiftool.exe -d %Y '-fileName<${Title} - $Author [$CreateDate]'.pdf -ext pdf
Though this will fail if any one of Title, Author, or CreateDate doesn't exist. If this command fails, it helps if you copy/paste the output and use the Code Button (https://exiftool.org/forum/index.php?topic=4888.msg69111#msg69111) on the output.