.
Firefox 19 uses an add-on which in turn uses HTML5 to render pdf files,
and it does a beautiful job. IceWeasel 10 does not reject this add-on,
but seems not to be able to understand HTML5, and does a poor job with pdf
files as a result.

There may have been an Adobe Acrobat add-on at one time that would serve
IceWeasel, but currently a Documents-Online-Viewer add-on seems the only
thing available to IceWeasel 10, and it does not do a really good rendering
of pdf in some instances: such as a WireShark user manual.