[2b3a51]

Try

    groff -ms -Tpdf example.groff > example.pdf

The difference is the use of the ms macro package. That package generates page breaks and makes assumptions about the page size. -Tpdf will typeset your text using proportional fonts, justification and so on.

The previous poster's command generated nicely justified text in the terminal (or redirected to a file).

[b3lm0nt]

Ah, this explains it. I had a feeling I was missing something in my less informative response.