How do I get Hazel to recognise comments in PDFs?

I'm trying to set up some Hazel rules to allow me to:

Open a PDF in ReaddleDocs (on the iPad) from my iDisk
Annotate the PDF (e.g.: add a note "Paid BPay #receipt-number")
Have ReaddleDocs sync that file back to my iDisk
Have Hazel recognise the comment has been added and do stuff with that file

At present, it seems that Hazel will only recognise words in the 'original' PDF, and ignore notes that have been added. I can use grep to find that the pattern is in the document. I have set up a rule "If contents contain 'Paid BPay'", which is supposed to set the label at this time. When I use the "Preview Rule Matches..." option, the document is not matched.

Do I just need to bite the bullet and write a cron job to do this one for me using grep?

Is that note being indexed by Spotlight? In Finder, if you select the file and do "Get Info", does it appear under "More Info" and if so, what's the name of the field?

No, the notes are not indexed by Spotlight. They do not show up in "Get Info", nor does the document show up if I use Spotlight to search for "Paid BPay".

I'll proceed with writing up a script to poll my iDisk, hopefully I can watch for "new" files, tag them as appropriate, and let Hazel take care of the rest. I've also contacted Readdle with a feature request for OpenMeta support in their ReaddleDocs product, but having ReaddleDocs be able to tag my documents is really pie in the sky dreaming

The ultimate goal here is to have Hazel find documents on my iDisk that I've updated in a particular way and file them away in the appropriate folder on my Mac. I can change the "updated in a particular way" part as required.