more standard and more robust, following hints on the Net;

--- a/src/HOL/Examples/document/root.tex	Mon Sep 28 16:23:15 2020 +0200
+++ b/src/HOL/Examples/document/root.tex	Mon Sep 28 16:43:49 2020 +0200
@@ -1,6 +1,6 @@
 \documentclass[11pt,a4paper]{article}
+\usepackage[T1]{fontenc}
 \usepackage[utf8]{inputenc}
-\usepackage[T1]{fontenc}
 \usepackage[only,bigsqcap]{stmaryrd}
 \usepackage{ifthen,proof,amssymb,isabelle,isabellesym}
 

--- a/src/Pure/Examples/document/root.tex	Mon Sep 28 16:23:15 2020 +0200
+++ b/src/Pure/Examples/document/root.tex	Mon Sep 28 16:43:49 2020 +0200
@@ -1,6 +1,6 @@
 \documentclass[11pt,a4paper]{article}
+\usepackage[T1]{fontenc}
 \usepackage[utf8]{inputenc}
-\usepackage[T1]{fontenc}
 \usepackage{ifthen,proof,amssymb,isabelle,isabellesym}
 
 \isabellestyle{literal}