Sorry for the late reply. I did get it working, but I basically used three workflows. The first one is the standard "Approval - Sharepoint 2010" globally reusable workflow. After it gets approved here, I have the conversion workflow kick in. I have that one as:
Wait for 'Approval Status' to equal '0;#Approved'
If 'Current Item:Approval Status' equals '0;#Approved'
and 'Current Item:File Type' not equals 'pdf'
Convert 'Current Item' to 'this url' using 'the same file name'...
Once the conversion process completes I have the third workflow setup to run when a new item is created to approve the pdf:
If 'Current Item:Approval Status' equals '2;#Pending'
and 'Current Item:File Type' equals 'pdf'
Set content approval status to 'Approved' with 'comments'
I tested on a couple documents, and everything was converted and approved. I haven't done any detail testing. Is there anything you can see that I would need to change? I know I'll need to tweak it if we ever add pdf documents, but I don't see us doing that any time soon.