==== Install okular on Windows ====
Requirements:
  * Admin privileges are not required

Steps:
  * https://okular.kde.org/download/ -> Download -> Windows -> Click the link "release nightly build"
  * This will take you to https://binary-factory.kde.org/job/Okular_Release_win64/
  * Download the .exe file (ex:- https://binary-factory.kde.org/job/Okular_Nightly_win64/lastSuccessfulBuild/artifact/okular-master-1209-windows-msvc2019_64-cl.exe -> https://build-artifacts.kde.org/binary-factory/Okular_Nightly_win64/lastSuccessfulBuild/okular-master-1209-windows-msvc2019_64-cl.exe -> okular-master-1209-windows-msvc2019_64-cl.exe )
  * Double click on the exe file; Select the default values.

Okular will be installed in C:\Users\<USERNAME>\AppData\Local\Okular\bin\okular.exe

==== Annotations ====
tags | Draw a rectangle, highlight an area
<code>
Tools -> Review (F6)
</code>

Works in okular 1.3.2, Debian Buster.

<code>
 % dpkg -l okular | grep ^ii      
ii  okular         4:17.12.2-2.2+deb10u1 amd64        universal document viewer
</code>

Ref:- 
  * http://docs.kde.org/stable/en/kdegraphics/okular/annotations.html
  * https://superuser.com/questions/349000/how-do-i-annotate-a-pdf-file-in-ubuntu