Found out recently that DTPO has an excellent function where you can index items placed inside Dropbox. Works perfect on my computer but does it also work when syncing with my DTTG on iPad?
Should I make replicants of the files inside Dropbox to move the physical files to inside my DTPO?
Read manual as usual and this forum but did not find any relevant info.
Does it work… how?
Can I open documents like .pdf´s stored in Dropbox on my iPad?
Playing with the Beta-version so did not want to erase it and reinstall the normal one before I know.
You can import Dropbox documents into DTTG using the share extension, but if the documents are already indexed to a DEVONthink database, why not sync them instead?
Ok sounds smarter to sync instead of index.
What is the best way to sync instead of index?
This is assuming that you have indexed the documents. If you are using DTTG 1.x, replicate the indexed Dropbox folders/documents to the Sync Group. If using the beta, perhaps this is a question for the beta forum.
Nope I mean the original 1.0. Perfect thanks!!
"Can I open documents like .pdf´s stored in Dropbox on my iPad?” :: No. You cannot access the files in Dropbox from within DTTG, even when indexing the files. They are copies synced into DTTG, not pointing to the Dropbox servers.
Ok will try to replicate them in some way then so the .pdf file physically is inside DTPO before syncing with DTTG.
Not necessary, unless you want to. You can index files from Dropbox normally if desired. I am saying that DTTG is a closed ecosystem. This means the indexed files on your iPhone / iPad in DTTG are self-contained at that point. They DO NOT point to Dropbox servers and you are NOT accessing them from Dropbox servers.
Ok, think I keep it as is for now. Reason why I use Dropbox is so both me and my wife can store invoices, titles etc. In Dropbox and both access them. We both use DTPO and index from there.
DTTG 2.0 Final version might be able to do what I want.
I haven´t read the part of the manual with sharing data between two DTPO users but that might be a solution as well. Right now Apple does not let two persons share iCloud easily so thats why we went with Dropbox as our common base for some stuff.
We both use the index function indexing Dropbox from both our DTPO and that works like a charm on our computers. But I don´t really have a big need for it on my iPhone/iPad but it feels like when you think you know all the possibilities with Devonthink - you realize it just started!
But wait, there is more 
if i understand your situation correctly, the solution is simple. it is basically the same as what i do with spideroak (secure dropbox alternative).
christopher-mayo.com/?p=2376
i index a single folder in spideroak, and all of the many subfolders automatically get indexed. these are treated as groups inside devonthink. it is pretty much effortless.
If the files are in Dropbox already, why not just use the Dropbox app on you iPad? You can use Dropbox’ Offline feature if you need access while not connected.