Hi Paul --
You can add any arbitrary text to your title(from a parameter, or if you're more creative, from a field). However, Tableau itself doesn't track that this 1st/2nd/3rd iteration/version/save on the report in a way you can easily get at it. Are you tracking that info yourself somehow?
Just want to be clear.
Maybe this workaround can help you for the issue i assume that this version control will be refreshed daily.
u can generate the pdf using tabcmd and add date at the back of the file like below.
tabcmd get "http://servername:port/views/folder/dashboard.pdf" -f "test%date:~10,4%%date:~4,2%%date:~7,2%.pdf"
change the link to your workbook view link and add ".pdf" at the back (-f) mean that you rename and save the file as test20140204.pdf.