Automation Direct doesn't like to make the manual to readily available as a way of discouraging unauthorized copying.
I would suggest that you upgrade to DirectSoft v5. The upgrade is like $195, there are a lot of feature upgrades, support for new PLC models, and bug fixes, and you'll get a (digital) manual. If your company won't cough up the $195, find out where the v4 software or v4 upgrade was purchased, from Automation Direct or from a VAR. That company should have a record of the sale and should be willing to provide a copy of the documentation.