PDFs that are in DTTG are easily opened by my other applications such as PDF Expert, GoodReader, Papers, Notebooks etc. The difficulty I am having is when I want to send these PDFs w/annotations back to DTTG. DTTG does not appear as an option in the “open in menu.” So when I have made annotations in PDF Expert GoodReader, Papers, and Notebooks all appear in the open in menu but DTTG does not. Is it possible to roundtrip a file back to DTTG? Do I need to reset DTTG?
My experience is that when this happens, and it happens with other apps also, is because you currently have more apps that can open a PDF than the 'Open In" menu of iOS can handle. I don’t know what that number of apps is, or if it is a fixed number, but try deleting some of your lesser-used PDF apps (one-at-a-time) and see if that helps.