Approving document in SharePoint

Our client uses SharePoint and he wants to have workflow of complex approving a word document.

For example, workflow steps are:
- Author prepares document.
- 1-st manager approves it
- 2-st manager approve it
- some actions and so on ...

I can use 2 ways to decide of this task:

1. To store document in SharePoint Library and use k2 for developing approving process. But in this case I can not prohibit changing the document body by Author during the process.

2. Do not use SharePoint Library during the process and put document to SP Library on the last step, when the document is already approved. But how I can upload .doc file to process? Which properties should I fill to have ability to attach document?

I have read documentation and k2-forum, but I did not find the answer.

Thank you