there is no way to see the text boundaries outlining the margins of a document in writer. the view -> text boundaries doesn't work. BTW, the little "L"s in the corners of the margins --- that's lame.
Already reported (and RESOLVED FIXED) as 'Bug 46073 - Page Layout Guides (margins, headers, footers) No Longer Visible'.
See also my answer on AskLibO → http://ask.libreoffice.org/question/3439/text-boundaries ;)
*** This bug has been marked as a duplicate of bug 46073 ***