[pdftk][] is a useful tool for manipulating PDFs.

Unfortunately, there's a [bug][] in [[Gentoo's|Gentoo]]
`app-text/pdftk` package.  The build eventually crashes with:

    g++ -DPATH_DELIM=0x2f -DASK_ABOUT_WARNINGS=false -DUNBLOCK_SIGNALS -fdollars-in-identifiers -DPDFTK_VER=\"1.44\" -Wall -Wextra -Weffc++ -O2 -I../java pdftk.cc -c
    pdftk.cc:60:39: fatal error: com/lowagie/text/Document.h: No such file or directory

Which is due to a bad `-m64` option brought in by `CFLAGS_amd64`:

    gcjh -force --classpath=":/var/tmp/portage/app-text/pdftk-1.44/work/pdftk-1.44-dist/java:." com/lowagie/text/Chunk
    gcjh: unrecognized option '-m64'

You can successfully install pdftk with:

    CFLAGS_amd64="" emerge -av pdftk

[pdftk]: http://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/
[bug]: https://bugs.gentoo.org/show_bug.cgi?id=254463