Trim margins of the entire document by command line (after TeX Live 2020 update)

Question

I'm used to compile my .tex files with this command:

pdflatex '\AtBeginDocument{\newlength\DX \DX=3cm \paperwidth=\dimexpr\paperwidth-\DX\relax \hoffset=\dimexpr\hoffset-.5\DX\relax \newlength\DY \DY=3cm \paperheight=\dimexpr\paperheight-\DY\relax \voffset=\dimexpr\voffset-.1\DY-.5\footskip\relax \RequirePackage{xcolor}} \nonstopmode\input{test.tex}'

I'll write it here in a more readeable way:

pdflatex '\AtBeginDocument{\newlength\DX
          \DX=3cm \paperwidth=\dimexpr\paperwidth-\DX\relax
          \hoffset=\dimexpr\hoffset-.5\DX\relax
          \newlength\DY \DY=3cm
          \paperheight=\dimexpr\paperheight-\DY\relax
          \voffset=\dimexpr\voffset-.1\DY-.5\footskip\relax \RequirePackage{xcolor}}
          \nonstopmode\input{test.tex}'

See Trim margins of the entire document (by command line)

But after the last update to the October release of TeX Live 2020 it doesn't work anymore.

This is a MWE. My file contains:

\documentclass[11pt]{article}
\usepackage{amsmath}
\usepackage{jheppub}
\usepackage{blindtext}
\begin{document}
\blindtext
\blindtext
\blindtext\footnote{\blindtext}
\end{document}

I want an output as if it were:

\documentclass[11pt]{article}
\usepackage{amsmath}
\usepackage{blindtext}
\usepackage{jheppub}
\usepackage[pass]{geometry}
\newlength\DX \DX=3cm
\paperwidth=\dimexpr\paperwidth-\DX\relax
\hoffset=\dimexpr\hoffset-.5\DX\relax
\newlength\DY \DY=3cm
\paperheight=\dimexpr\paperheight-\DY\relax
\voffset=\dimexpr\voffset-.1\DY-.5\footskip\relax
\begin{document}
\blindtext 
\blindtext
\blindtext\footnote{\blindtext}
\end{document}

but I don't want to change my .tex file. I need to do it by command line.

Now, after TeX Live 2020 update, I get:

where the trimmed margins are wrong. I think that the probles is caused by something in the jheppub.sty file.

You can find the jheppub.sty file here: https://jhep.sissa.it/jhep/help/JHEP/TeXclass/DOCS/jheppub.sty

Answer 1

With the new LaTeX \AtBeginDocument commands from the user ("top-level") are executed last, after all other \AtBeginDocument.

This means that if you change the page layout there, you are reponsable to set all relevant values. No code in graphicx or color or geometry will do it for you.

In your case you are missing to set the pdf page values:

\pdfpageheight=\paperheight \pdfpagewidth=\paperwidth

An alternative is to use an earlier hook:

  \AddToHook{begindocument/before}{<your code>}