data returned from cfpdf action=read

I'm trying to figure out how to determine if a PDF retrieved using cfpdf action=read has been flattened.

If I attempt to flatten an already-flattened PDF I get a "Source does not have any form. Cannot specify flatten for the WRITE action in the cfpdf tag" error.  So, I'd like to read a PDF and then only run the flatten code if it needs it.  But I can see from the variables returned from action=read how to determine that.

Thanks.

Matt