Why import an Open Office document into DW?
Via File > Import, Dreamweaver asks Word to convert the content to HTML then inserts that code into the page.
It's safer and more controllable to cut and paste the text from Word files into DW. You can do the same with Open Office.
When I copy and paste the text to the desired page, most of the formatting does not appear as it is within the Open Office document. Is there a way to avoid this?
Actually you really don't want formatted text brought in from Open Office or Word or any other app. Unformatted text plays nicer with HTML. Use CSS to style your text.
Dreamweaver formatting is totally different than that of a word processor. Word processors generally have access to hundreds ot typefaces and typestyles. Dreamweaver has just a few.
As such, I do what John does and copy and paste as plain text. And I'll do specific formatting as needed. You're not making a piece of printed paper here, you're making a web page. So the design work is more like page layout than it is a simple Word document.
The articles here used to be, either in a magazine or a Word Document (take your pick). I reset everything to make a web page, knowing that people don't read web pages, they tend to scan them. So I add interest with graphics and with design elements.