Wait until file is unused

[kinook]

Can't you launch Word and/or PDFCreator in such a way that it won't return/exit until it has finished? Otherwise,

1) As you mentioned, you could wait until the PDFCreator process exists, then wait until it goes away (using vbld_AppIsRunning in a Run Script step).
2) Try to rename or open the file (which should fail if PDFCreator is still writing it) until it succeeds.