How do you save .doc in iWork Pages?

Answer 1

Export it.

Exporting to Other Document Formats

You can share your Pages documents across different platforms by exporting them to other formats, such as Microsoft Word, PDF, or plain text. You can also save a document so it can be opened using Pages in iWork ’05 and iWork ’06.

"Importing a Document

You can create a new Pages document by importing a document created in another application, such as Microsoft Office 2007 or AppleWorks. Pages can import the following file formats: plain text (.txt), Rich Text Format (.rtf and .rtfd), AppleWorks 6 word processing (.cwk), and Microsoft Word (.doc).
As much as possible, Pages preserves the original document’s text, colors, layout, and other formatting options.
From Microsoft Word, you can import styles, tables, inline and floating objects, charts, footnotes and endnotes, bookmarks, hyperlinks, lists, sections, change tracking, and more.
From AppleWorks, you can only import word processing documents."