TextEdit: HOW DOES MY LETTER FIT ON A PAGE?

To see TextEdit's page boundaries, press Command-Shift-W (the shortcut for the Wrap to Page command) and the page margins will appear onscreen. Another thing that will make TextEdit behave more like the word processor it really is, is to go under the Format menu and choose Allow Hyphenation, so when a word extends to the page's edge, it gets automatically hyphenated and split by syllable to the next line, like you'd expect in a standalone word processor.