The Documentation System is what this documentation was created in.
To being making documentation for your project you first need to save your C4D file in a location on your harddrive.
Next you will need to create a database and folders to contain the images. This is done by pressing the "Create Database" button on the dialog. A new directory will be created along side your C4D file called "documentation". This will contain the database and some folders for your images, thumbnails and also a published folder which is where the final documenation will be placed when you press the "Publish" button.
Pressing the Add Section button will add your first page to your documentation. These are called sections rather than pages, since pages can also include information from other sections.
Pressing Add Section again will add another section at the same level as this one.
Pressing Add Child will create a new section underneath the currently selected one.
With these two buttons you can easily fill out your documentation structure.
The text for the page is entered using a Markdown lanaguage. This makes it easy to specify bullet points, lists, and titles for your pages.
You can read more about the Markdown from here
The preview button will display the currently selected section in an html dialog. This view will update when you type in to the content of the section and then click out of it so that it looses focus. The html view will then update to reflect the changes.
This will write out the html files to a "documentation/published" folder located next to your c4d file. This folder contains everything you need to upload to your webserver. It will then launch your default browser to display the documentation.
In this area you can drag and drop an image from disk to add it to the documentation system. After dropping the file a unique ID will be generated and added to your clipboard. You can then paste that into your documentation content to indicate where the image should appear.
You can also drag and drop tools from Cinema 4D into the drop zone. To do this you right click on the UI in Cinema 4D and choose "Customize Commands". Next scroll through the list of available icons in Cinema 4D until you find the one you want to use. Then simply drag and drop it into the drop zone. A special code will be generated for this icon and it will be added to your clipboard. You can then paste it directly into your documentation.
When you publish out your documentation the Icons are copied and exported out during the publishing. This means it will use the latest icon that you have in C4D when publishing the help files. That way you can keep updating your icons without having to worry about keeping the documentation in sync.
You can also copy an image to your clipboard and press the Paste Image button. This will create a copy of the image and save it to your documentation system. It will then create a a unique code and copy it to your clipbaord. You can then paste this code in your documentation to display the image a the correct location.