When printing some PDF file generated by pdflatex, either with xpdf
or via pdftops + lpr, a horizontal line is missing from the output
(only on the paper, not on the screen). There's no such problem with
lpr run on the PDF file directly. I don't have any idea where the
problem comes from. I'm reporting the bug against texlive, assuming
the original problem might come from it, since the bug appears with
both xpdf and pdftops + lpr.

Note: pdftops comes from poppler-utils 0.12.2-2.1.

With the attached (very short) testcase:

$ pdflatex missing-line.tex
$ lpr missing-line.pdf
-> OK
$ xpdf missing-line.pdf
-> When printing, the bottom line of the rectangle is missing.
$ pdftops missing-line.pdf
$ lpr missing-line.ps
-> Same problem.