Hi lmagalhaes,
I am a wire design engineer, and, the program that you are talking about is non-trivial, as it creates a netlist of interconnections, devices and parts. Each device has a reference designator as an identifier that can be created singularly or multiple times in a wiring diagram extracted from the same part information and is comprised of a sophisticated database. I am not familiar with Altium, but I have used a very sophisticated program for years in my job that is supplied by Siemens called Mentor Graphics Capital and it is very complex (and very expensive). There may be some free ones out there, but i am not aware of them.
With that said, in lieu of such a program, you could create a netlist with a spreadsheet and accomplish the basis for the wiring diagram design by identifying each connector on your device and creating the pin to pin spreadsheet in its' simplest form of:
FROM Ref Des PIN # WIRE Gage SIGNAL TYPE TO Ref Des PIN#
Each of the above would be separate columns headings. Of course, as engineers, we want every detail of the design put into this spreadsheet, so you could add the left hand side connector part information from your device as detailed as possible and then, later in the spreadsheet, go from the opposite direction in order to identify the right hand side back to the original connector on your device. Also, you could add as many headers (columns) as desired in order to finely define this circuit. This would be your wire list and a diagram could easily be created from this information with the correct software and you would not need be involved (except for clarification).
The other method, if your device is small (less than 500 circuits? maybe?), and if your signal types are similar or the same (such as MAINS, CONTROL, and/or RETURN), you could simply create a ladder diagram of your controller in the machine system, which includes the entire schematic design. This is dependent on how simple or complex your wiring will be. If this is all power and control circuits, this is what I would recommend. You could use AutoCad or any other flat drawing system to accomplish this.
Wiring design is a multi faceted discipline and can be somewhat simple, as in the case of a ladder diagram, or very complex as in netlists and multi-cored wires with many different functional characteristics, depending on the signal types. I can't even begin explaining the complexities of designing wire systems in this format, on this forum. But this is a 10000 meter view of such a system.
Hope this helps...