I have a solution. However this might not be the most elegant way.
You have to define your own numbering scheme for hyperref so that each number is unique:
\listfiles
\documentclass{book}
\usepackage{amsmath}
\usepackage{hyperref}
\usepackage{cleveref}
%%% define a new counter and use it for \theHequation which hyperref uses for the links
\newcounter{Hequation}
\renewcommand{\theHequation}{\thechapter.\arabic{Hequation}}
\makeatletter
\g@addto@macro\equation{\stepcounter{Hequation}}
\makeatother
\begin{document}
\begin{equation}\tag{first}\label{eq:first}
\text{First equation}
\end{equation}
\begin{equation}\tag{second}\label{eq:second}
\text{Second equation}
\end{equation}
\begin{equation}\label{eq:firstreal}
\text{First equation without tag}
\end{equation}
\begin{equation}\tag{third}\label{eq:third}
\text{Third equation}
\end{equation}
\begin{equation}\label{eq:secondreal}
\text{Second equation without tag}
\end{equation}
\begin{itemize}
\item A reference to~\eqref{eq:first}.
\item A reference to~\eqref{eq:second}.
\item A reference to~\eqref{eq:third}.
\item A reference to~\eqref{eq:firstreal}.
\item A reference to~\eqref{eq:secondreal}.
\end{itemize}
\newpage
For scrolling purposes.
\end{document}
As you can see \equation has to be redefined as well. Then equations with and without \tag can be mixed-up without any problems.
Best regards
Martin
I'm not sure if an answer is still of interest. Anyway:
1) I would strongly advise to use the pdfx package:
\usepackage[a-1b]{pdfx}
2) The error in the pdfx package is caused by the way how the timestamp is put together. Depending on your timezone (e.g. UTC+1, UTC-1, etc) you have a different sign there. This causes the issue.
Use of \getTZh doesn't match its definition.
You therefore need to put the pdfx.sty in your working directory and need to adjust that specific line accordingly:
\def\getTZh +#1#2{\edef\xTZh{#1#2}\getTZm} % change - to + if error occurs (due to timezone)
...
T\xHour:\xMin:\xSec+\xTZh:\xTZm}} % change - to + if error occurs (due to timezone)
Alternatively, you may change the timezone of your system.
3) pdfx automatically loads the hyperref package, too. If you want to have a customized hyperref setup, you can use:
\hypersetup{
unicode,
colorlinks=true
}
In addition to that, you need to provide a color profile and a valid xmp file. Information on this can be found in the pdfx manual. This solution relies on pdftex.
I'm not aware of any solution using dvips.
Best Answer
According to the documentation,
should do the trick.