Had the same issue with DTTG and PDF Expert 6. Seems to me it is a PDF Expert 6 problem. In fact, if I use the PDF Expert document picker to take a file from DTTG and made an annotation (whatever type) it work, but just the first time.
If I leave PDF Expert open and pick again the DTTG file and made another annotation (whatever type) it doesn’t sync back to DTTG.
If I want to add another annotation to an already annotated file I am forced to close PDF Expert and reopen the file.
Therefore, it seems to me that PDF Expert save the PDF in the cache and this create some problems with the overall syncing process.
Has someone found any solutions? or alternative? Sincerely I would prefer not to use the internal PDF annotator…