if you have a server someplace and can write VB.Net ...
Send the PDFs up to a server webservice with a random queue number, stitch them together with ItextSharp.
From the tablet check the queue number status every 10 seconds until the job is done (or has tried too many times.)
Have the service send back "its done" or whatever to the tablet in the queue check, then pull the results back down...
Its not impossible, but it takes a bit of code...
If you get really fancy, you send data to SQL via web services and have your SharePoint server render pdf reports in fine style that are delivered back to the app.