iOS 4.2 on iPad introduced AirPrint. When coupled with Ecamm’s Printopia, and one of the DEVONthink Pro folder actions, you can “print” a PDF directly to the global inbox. Or modify the action to send the PDF to the database and group of your choice.
Printopia’s Send to Mac feature puts PDFs of documents printed from iPad Mail, Safari, iWork, etc., into ~/Documents/Printopia. Add one of the DEVONthink Pro folder actions to that folder (import or index are available actions) and you’re done. Look up Folder Actions in Help for more information. Modify the folder action (in Automator) and customize it for the target group. All this only works on your local network.
Printopia also has a Send to Dropbox on Mac action, and with that you can round trip your printed PDF into DEVONthink To Go or elsewhere on your iPad.
Thank you, ‘korm’!
Side note: Neither ‘korm’ nor DEVONtechnologies has any affiliation with Ecamm.