Can you tell me if any of your scanning works? Can you scan the same image on a smaller document or at a lower resolution?
I have a scanning profile configured on my 700, so that all of my scans are 600dpi at 11X17, I then just crop the file in Photoshop.
I have my scanning profile configured to scan to TIFF, or JPG, but not to PDF. I believe it requires having a server onto which, the 700 can deposit the scanned files. Ours is configured so that it scanns the file, and then deposits it via FTP onto our file server.
In short, your 700 should be able to scan at 600DPI up to the full size of the scanner platen.