In OPDK 15.01 you can recover a lost system admin password by following these steps. Note: you will have to know your LDAP system password in order to reset your system admin password.
Step 1: Run the following command to update the system admin password in OpenLDAP:
ldappasswd -h localhost -p 10389 -D "cn=manager,dc=apigee,dc=com" -W -s <new_password> "uid=admin,ou=users,ou=global,dc=apigee,dc=com"
Step 2: (OPDK 15.01 or newer) Run chpasswd-system.sh with the new password you entered in step 1 as the existing and new password. The chpasswd-system.sh script is located in //apigee4/bin directory. This script would update the apigee.conf file for the UI to the new password you have setup in OpenLDAP.
For OPDK 14.07 or older: use the EncryptUtil steps per this article to update the apigee.conf, not the chpasswd-system.sh script :
http://community.apigee.com/articles/1916/opdk-how-to-manually-update-ui-credentials-for-acc.html