Packages scrpage2 how to force header and footer on every page

Question

I want to have footers and headers on every page of my report (which I do not want to change). But the header does not appear when I start a chapter or for other Chapter like parts (e.g. table of contents). I tried to draw a line on every page into the header instead of using the scrpage2 header, but as far as I can see the missing chapter headers in scrpage2 are created by using white colour, hence it does not work as my black line gets overlayed by the white line.

Question: Is there a way to force the scrpage2 headings to appear on every page?

Here is a minimal working example to illustrate the problem with the chapters.

\documentclass{report}   
\usepackage[nouppercase,headsepline,footsepline,plainfootsepline]{scrpage2}
\pagestyle{scrheadings}
\clearscrheadfoot
%\ihead{(Document title)}
\ofoot[\pagemark]{\pagemark}% Optional argument controls chapter-starting pages

\begin{document}

\maketitle
\newpage
\chapter {Introduction1}
\newpage
\chapter{Introduction2}
\newpage
Test
\newpage
\end{document}

Answer 1

Chapter pages uses page style plain by default. If there should be a line below of the header on plain pages too, add option plainheadsepline.

Note that package scrpage2 is outdated. So here is an example with its successor scrlayer-scrpage:

\documentclass{report}
\usepackage[
  markcase=noupper,
  headsepline,plainheadsepline,
  footsepline,plainfootsepline
]{scrlayer-scrpage}% activates pagestyle scrheadings automatically
\clearpairofpagestyles
\ihead*{(Document title)}
\ofoot*{\pagemark}

\title{Header Footer}
\author{adp2018dik }
\date{October 2018}

\begin{document}
\maketitle
\newpage
\chapter {Introduction1}
\newpage
\chapter{Introduction2}
\newpage
Test
\newpage
\end{document}

Result:

Note that \ofoot*{\pagemark} is a short version of \ofoot[\pagemark]{\pagemark}.

---

The same with the outdated package scrpage2:

\documentclass{report}
\usepackage[
  nouppercase,
  headsepline,plainheadsepline,
  footsepline,plainfootsepline
]{scrpage2}
\pagestyle{scrheadings}
\clearscrheadfoot
\ihead[(Document title)]{(Document title)}
\ofoot[\pagemark]{\pagemark}

\title{Header Footer}
\author{adp2018dik }
\date{October 2018}

\begin{document}
\maketitle
\newpage
\chapter {Introduction1}
\newpage
\chapter{Introduction2}
\newpage
Test
\newpage
\end{document}