How do I use REVTeX4 with PCTeX 6?
Install the latest version by downloading the REVTeX distribution (https://authors.aps.org/revtex4/revtex4-1.zip).
This archive contains a revtex4-1 folder. In this folder is an archive called revtex4-1-tds.zip. Open this archive and copy its bibtex and tex folders to PCTeX's texmf\bibtex and texmf\tex folders. You will probably get a warning that there are already folders called bibtex and tex. You should tell it Yes to continue copying. This should install the files in the correct locations and REVTeX should now be installed in PCTeX.
The revtex4-1\doc folder contains a couple of samples in the doc\latex\revtex\sample\ folder.
The basic format of a REVTeX document is:
\documentclass{revtex4-1}
\begin{document}
\end{document}
When you typeset the document, it will probably not be able to find some packages on the computer and will offer to locate the package for you. You should answer Yes to find the package and then click Yes to install the package.
You will need to typeset again for the cross-referencing to be correct.