If \citeauthor (or any other command) is defined with \newcommand or \DeclareRobustCommand and has an optional argument it can't be expanded when PDF strings (PDF bookmarks etc.) are generated. The same is true if \citeauthor is defined as a \protected command (e.g. via \newrobustcmd of the etoolbox package). In all these cases, the hyperref package outputs a warning message similar to:
Token not allowed in a PDF string (Unicode):
removing `\citeauthor' on input line 378.
You can add an expandable substitution for \citeauthor to the hook \pdfstringdefDisableCommands which is only evaluated in the context of PDF-string generation, e.g.:
\pdfstringdefDisableCommands{\def\citeauthor#1{#1}}
\begin{document}
...
As a result, the warning message disappears and you get the bare citation key in PDF bookmarks. Obviously, this is not an optimal solution, but better than nothing.
Whether it is possible to really get the author name in PDF bookmarks depends on the implementation of \citeauthor. Clearly, if \citeauthor is a complex command it is difficult or even infeasible to add a usable substitution to \pdfstringdefDisableCommands that is simple enough for PDF-string generation. In particular, the latter might be the case for \citeauthor as defined by the biblatex package.
Finally note that the xparse package (part of the l3packages collection) provides the command \DeclareExpandableDocumentCommand which can be very useful for adding command substitutions to \pdfstringdefDisableCommands.
\texorpdfstring{<..>}{<..>}macro to use a different version for the PDF bookmark entry. – Martin Scharrer Jul 21 '11 at 14:21\citeauthor? A minimal example would be welcome. – Bruno Le Floch Jul 28 '11 at 09:10