If the “parts” are interspersed all over the document, you need to have Hidden Paragraphs and/or Hidden Text (inside a paragraph) fields controlled by a conditional variable.
This is quite tricky, needs some preparatory work but is extremely powerful. You set the variable to some value and your text adapts accordingly. You can have as many “versions” as you need simply by changing the variable value. It could also be easier to use several variables in case you have sub-versions.
Another possibility, provided your document is very consistently styled, i.e. absolutely no direct formatting is to change the template upon which you base your document. Some styles receive property Hidden if the corresponding paragraph should be skipped in this version. This approach also allows you to layout differently your versions, e.g. standard portrait for customers, landscape with additional comments or e-book for staff. You are only limited by your imagination.