inputenc Error: Unicode char \u8: not set up for use with LaTeX

The error you get is due to a "no-break space" character, according to what I can gather by copying an pasting your message.

This character is not usually set up by the [utf8] option and it's invisible to many editors, so it can slip in a document without the typist knowing it.

Solution: add in your preamble

\DeclareUnicodeCharacter{00A0}{ }

if you don't mean to type a no-break space, or

\DeclareUnicodeCharacter{00A0}{~}

if you want that the character stands for what its name says.

UPDATE

Recent (after 2015-01-01) versions of the UTF8 configuration file for inputenc do define U+00A0 as \nobreakspace, so this should be of no concern, now.

As this is one of the top google hits for this error message, here's a more general answer with an example:

The cause is a unicode character in one of your input files that isn't mapped to an output. This may -- especially if you're using the (unicode-supporting) biblatex/biber system -- be in your bibliography. This is a good place to look for errors as .bib files downloaded from publishers website are often malformed. You can tell if the error comes from the bib file - the line number in the error message will be that of your \end{document}, which makes tracking down the actual error rather tricky (inspecting various aux files doesn't appear to help).

Some of these errors are subtle, like the non-breaking space in the question, or the hyphen (U+2010) character given to me by one journal, which looks identical to the hyphen-minus produced by the keyboard.

Copying the character after the hyphen and searching for it should help - unless your command window or editor "helps" by converting it to the more common equivalent or replacing unicode with blanks - in that case copy it from your .log and search all the input files.

(I'm happy to expand this in response to comments or watch it grow -- it's just an attempt to be helpful to searchers)

\usepackage[utf8x]{inputenc}

Ubuntu:

You must install texlive-latex-extra before use it.

Fedora:

You must install texlive-collection-latexextra before use it.