Content type with multiple different flavours I want to create content type (document) with title, comment and file attachment (PDF or doc). I don't want to create different content types (for each document type form, policy, abuse etc..) because if i need to add/remove/change field in it it's need to be repeated on all content types. I'm thinking about taxonomy but I'm not sure.

What's the best solution for one content type with multiple different "flavours"?
You can use taxonomy to categorize the content. If you want categorize the content like form, policy, abuse etc... create a taxonomy vocabulary name as Document Type then add form, policy, abuse etc... as terms in it. Then Add a term reference field(in D7) in manage field settings. And also you can use Conditional Fields for display fields according to the document type.