The functionality that the ITP/Server offers needs an account to run with. The account can be changed on the DP Manager tab of the ITP/Server Administrator.
To allow a logon account to run an ITP/Server Document Processor, this account needs the right to logon as a service. See the paragraph "Possible error: Failed to assign the 'Log on as a Service' right to the user" above for details on how to assign this right by hand.
Except for the 'log on as a service' right, a fast path to make the account have sufficient authorization is to make it local administrator on the machine(s) running ITP/Server. Furthermore we advise to select an account for which the password does not expire. Refer to Dialog: Set UserId and Password for more details on the specific rights required for this account.