I'm not sure what truncated text you have in mind here.  But if you select the text pane and choose ⌘-P, you can print the text to PDF in the usual way.

From v6.0, the text uses essentially the same methodology for RTF layout that is seen in TextEdit. The old $LeftMargin and $Right margin exist in (old(er)) TBX documents only for use with pre v6 Tinderbox.

By default, Tinderbox $text in a new note has a fixed left and un-set auto-wrapping right margin. However, if you copy/paste from an RTF source that does has a fixed page width/margin, the pasted data will respect the source's** formatting and may result in a fixed note text width and/or right margin. Each paragraph in v6 $Text may have a discrete style (font, width, tabs, etc.). The cocoa framework's supplied management for this is pretty lousy and poorly documented.

The easiest want to spot such non-default page style is to turn on the note's text pane ruler ([Opt]+[Ctrl]+R) and click in each paragraph noting margin/tab settings.  

If you have odd margins like this as a result of pasting, select the $Text (or affected sections within it) and use menu Format -> Style -> Reset Margins.

** To strip all such formatting in a paste, use 'Paste and Match Style' ([Cmd]+[Opt]+[Shift]+V). This results in all formatting (colour, fonts, margins, tabs, line spacing, etc.) being stripped. Only the text characters are pasted (including white space and line breaks).

Pro tip: when pasting into Tinderbox from other apps always use Paste and Match Style unless you definitely know you want any source format. It's often easier/quicker to stick back in a bold heading than it is spending hours trying to fix imported non-matching paragraph styles (for which the controls - derived from the Apple frameworks they use - are not very good IMO). The latter's not Eastgate's fault, the frameworks control what's possible and, in the round, aide lots of other good things unrelated to margins and printing: it's a matter of balance. So, if importing, try to get in the habit of using Paste and Match Style!

Edit: I've updated the aTbRef page 'Working with $Text: support for styled text'. Remember in most cases you probably want 'Paste and Match Style' instead of 'Paste' when importing text via a copy/paste

I tried the recommendations listed above, and my success rate has not produced the desired results.  So far, resetting the margins, paste and match style, and checking for irrelevant tabs fail to correct the lopsided margin issue. I also created a new document, added a few new notes with cut-and-paste text using "paste and match style," and the results are the same. Any other suggestions as to what might be the culprit?