Add a note on older version of pandoc

Author: kasper

Documentation/manpages/tool/README.md

@@ -26,3 +26,17 @@ sudo pip install pandocfilters
 git clone https://github.com/dotnet/cli
 ./cli/Documentation/manpage/tool/update-man-pages.sh
 ```
+
+The version of pandoc is printed in first line as code comment in `.1` (manpage) files.
+If your version of pandoc is older than (or even equal to) the last modifed version,
+please install the latest stable version of pandoc from https://github.com/jgm/pandoc/releases (deb file for Ubuntu):
+
+```sh
+wget -q https://github.com/jgm/pandoc/releases/download/$pandocVersion/$pandocVersionedName.deb > /dev/null
+# or
+# curl -sSLO https://github.com/jgm/pandoc/releases/download/$pandocVersion/$pandocVersionedName.deb > /dev/null
+sudo dpkg -i $pandocVersionedName.deb
+rm $pandocVersionedName.deb*
+```
+
+after that update manpages by calling `update-man-pages.sh` script.