I've been working on a prototype with a manufacturing client who handles tens of thousands of digital files of all types - some quite large- per year- and would like to have an efficient system for storing them logically and securely and retrieving them.

We've had excellent results with the varbinary(max) datatype with SQL server, so storing them and retrieving them is easy and speedy, even for the really large ones.

Some of the PDF's are created by a .NET app we wrote, so categorizing and storing them is easy.

We're at the stage of designing an interface which allows the user to drag and drop files from other sources on to various spots on a winform, thereby categorizing the files before we put them in the SQL table for a later retrieval.

Dragging from the windows explorer or the desktop is easy and works fine.

The client wanted to be able to drag attachment from Outlook emails, and after some heavy duty research I learned that all things are not dragged and dropped the same way, but rather, some drag origins have different "formats" than others, and if you drag something over an object that is not "looking" for the format of the dragged object's origin, the cursor will become a crossed circle and the drop cannot occur.

For example, this code in the dragenter method of the control will look for any file from Windows Explore or the desktop:

if (e.Data.GetDataPresent(DataFormats.FileDrop, false) == true)
     {
       e.Effect = DragDropEffects.All;
     }

and this code will look for any file that began as an attachment to an Outlook email

  if (e.Data.GetDataPresent("FileGroupDescriptor"))
   {
      e.Effect = DragDropEffects.All;
    }

OK , with that long preamble here's my question:

The client uses Acrobat 8 to store several PDF's in one PDF, and would like to drag individual PDF's from that combined PDF on to the Winform to categorize them before storing them.
We can do it by dropping a single PDF onto the desktop and then dragging to the Winform but we want to avoid that interim drop.

For the life of me, I can't find out what to look for from that Acrobat 8 drag source. I've searched and searched and can find nothing. One solution might be to do it from Acrobat using the SDK but I'd love to avoid that.

The basic app uses Winforms, but if WPF or something like it could handle this better, I could do that if need be
Any tips, hints or clues will be appreciated!!!