warning with hyperref package

Question

I have met warning:"Package hyperref Warning: Composite letter `\textdotbelow+u'" when i use this code to create a bookmark

\pdfbookmark{\contentsname}{Contents}

I don't know the reason for this warning, how to avoid and fix the warning.

Answer 1

Pass the unicode option to hyperref:

\documentclass{article}
\usepackage[utf8]{vietnam}
\usepackage[unicode]{hyperref}
\begin{document}
\pdfbookmark{\contentsname}{Contents}
\tableofcontents

\section{a}
\end{document}

Without the option I indeed get the warning

Package hyperref Warning: Composite letter `\textdotbelow+u'
(hyperref)                not defined in PD1 encoding,
(hyperref)                removing `\textdotbelow' on input line 5.

The warning disappears with that option. This should be independent of the input encoding chosen; I've tried with viscii, tcvn, vps, and utf8x

Answer 2

use

\pdfbookmark{\texorpdfstring{Contents}{\contentsname}}{Contents}

For Contents In \textorpdfstring you can use any translation without special characters which are not possible in the bookmarks of a pdf file, like your u with a underdot