I have not tested it, but I think if you open IIS and go to the AuditTrailConfig Virtual App, then select .NET Users and add the users there.

Otherwise, in the "\Program Files\Laserfiche\Audit Trail\WebAuditConfig\Web.config" file, you can find <configuration><appSettings><add key=AdministratorGroup value="S-..." />

This setting value equals the SID of the local administrators group on the IIS Server.  You could potentially create a Domain group for LFATAdiministrators, have the domain administrators group as a member and then all of the non administrative domain users that you want to allow access added as members and change the above setting value to the Sid of your domain group.  You would also need to make sure that the domain group had permissions to the Windows path "\Program Files\Laserfiche\Audit Trail\WebAuditConfig"