> I have a problem with the definition of the page margins in a LyX > document.. In particular, I would like to create a book-style > document, where the internal margin is always a bit bigger the the > external one so that once I print and bind it, the document will be > easily readable.
Choose Document -> Settings. Choose "Page Margins" (in left list). Uncheck "Default Margins". Set any as desired. Click Ok or Apply. (Maybe the defaults are good enough already.)