Notepad++ prints texts with spelling errors underlined. Quite very weird, but true.
Fortunately, you can workaround this problem by using quick serie of keyboard shortcuts.
Here we go:
(assuming that you're going to print on default or previously used printer)
This will: disable spelling errors underline, print the document and re-enable spelling errors underline again.
Another solution is to install additional dictionaries and then set Plugins > DSpellCheck > Settings... > Language to
Multiple Languages.... However, using too many languages may slow down your Notepad++.