Problem: Make little sense, but impact readibility

The border downgrade the readibility of documents. Nowadays more and more users just read the documents in computer screen, rather than print them out. The visible border disturb users at most of time.
When users create tables, the bordes of documents and tables will be overlaped. This will also cause there are so many things in documents which track uses' eyes.
Users can have the clues of the real border of documents via the rulers. The grey(or other colors) line is not must-have for users.

Competitor Study

MS Office 2003/2007/2010 : Put marks on four corners of page, to show the boder of documents.
MS Office 2008 : Put nothing within the page to show borders. Users can get the clues on page rulers.
Apple iWorks 2008/2009: Put nothing within the page to show borders. Users can get the clues on page rulers.

Put cross mark on the corners of editable area of the page.