How can I create different documentation from one source?

To produce two types of documentation such as documentation for internal and for customer use from only one source file:

Use other sections for each version.
Do not export the sections you do not want to include in the current version.
Label text parts and exclude this text in the current configuration.
Use topics or documentation snippets and exclude them in one configuration.

To use sections for conditional text

For example, assume you have a topic with ID "Overview", which contains both comment and specific information:

  @@Overview
  This is the overview for my project, it contains
  information on the architecture but nothing specific
  to a certain SKU.

  Professional:
  The professional version of the product can do this and
  this.

  Enterprise:
  The enterprise version is the full product, which does
  more then the professional version. Therefore this
  information goes into the enterprise documentation
  only

Add two sections to your project named professional and enterprise (with starter strings set to the same) on the Sections page, and enter all specific information for all topics into these sections.
Create one professional and one enterprise configuration.
In the professional configuration omit the enterprise section and in the enterprise configuration omit the professional section on the Files & Format > Sections page.
On the Project tab, in the Build group click the arrow next to Build , and then click Build All .
Both documentations are created.