I can’t Clip pdf (in mail) into DTTG. Url Clip worls Fine. Id that the expected behavior?
To save a PDF from iOS Mail to DTTG, press and hold the PDF preview in Mail and then choose DEVONthink from the “Open In…” selections
this is how I finally do it. It’s just a bit irritating to see the clip to DT icon. sorry for the mc ad 
Unfortunately Mail is not the best app when it comes to support for data sharing. Great that it works for you now!