It's all in the Help button at the top of your Trainz screen.
I printed it out and then found it was huge, a whopping great mass of paper and I think in all the years I have only looked through it twice, I just use the help button - or if really stuck - post on here.
The printout is now gathering dust somewhere...
You do not have to d/load this and any other TRS2004 manual, they are all in your installed TRS04 folder in the "Docs" folder or also possibly on your install CDs/DVD. All you need is the Adobe PDF reader to read these.