Smaller Margins for Plain Text in TextEdit

The usual advice for changing TextEdit's margins only works for RTF documents. It is also possible to change the margins of plain text documents, by scaling the content of the page (you'll need to adjust your text size to match).

In the print dialog box:

• in the Paper Size pulldown menu, choose "Manage Custom Sizes..."
• create a new custom size that is larger than your real paper, but in the same proportions (8.5x11" or 21x29.7 cm)

Then, in the second pulldown, "TextEdit":

• choose "Paper Handling"
• check "Scale to fit paper size"
• choose your real paper size

When you print, your margins will be smaller.

From a thread in Apple's discussion forums.