Read it again. What that page talks about is relabeling the "Abstract" property as something like "Client Name" and then copying that to use where you want the client's name. It has only one purpose. You have to use different content controls for different fields. The "document properties" you are already using are content controls that are already mapped. You can change their names.

The key is that by using mapping, you can have as many of these as you want without going through the "document properties" menu. You can have different kinds of content controls as well.

Read the articles. Take the time to learn this stuff and decide what will work for you. There are a number of options.

Start by learning about Content Controls. The content controls can be found on the Developer Tab.
Take a look at the Paste as Link option mentioned above and decide if that will work for you. It is the simplest.

If you want to be able to change each item anywhere in the document rather than in just the first spot, then you will need mapped content controls. Again, the ones you are using are a special case of mapped content controls. If you create your own, you can have as many as you want. The easiest way to map content controls is to use Greg's utility to insert the controls.

There are other ways of replicating data in a document discussed in one of the articles. Those work in earlier versions of Word as well.