Hi @all, 
thank you so much for providing such good help. 
First of all:
Here“s some info:
Xournal is a program for the simple creation of notes, digital notebooks (e-journals) and sketches, which can also be used to edit PDF files.
It behaves like an image editing program that places a transparent level on a background on which you can write and draw.
Data is stored as a file with the .xoj extension.
This can be provided with a PDF file as a background. There is also a function to export as a PDF file.
The program is particularly practical when using a graphic tablet. Since the graphics library GTK+ is used for the interface, it can also be used under Xfce, Mate and LXDE in addition to GNOME.
Functions:
- Pen tool
- etching tool
- Font tool
- Text highlighting
- Outline detection
In an existing journal, further pages can be inserted via āPage - New Page before / afterā
(from: Xournal āŗ Wiki āŗ ubuntuusers.de # in German, translated via āfirefox translationsā add-on )
Further reading:
@nevj :
That may very well be the case, Neville. 
I“ll ask my friend about it next time we talk again.
Sounds like a very good idea. That I will try, of course.
Thanks also for the links, Neville. I“ll look up the information provided by them.
This could be verified, can“t it?
⦠by checking the exif data wit exiftool
before and after rotation and then compare the values 
@daniel.m.tripp:
That“s certainly a promising command. Thanks Dan.
I used the mogrify
command in the past, but not the -rotate
option. I wouldn“t have thought of that, I have to admit.
I believe I used the command for resizing image files.
Well, not on regular basis, I guess. But that doesn“t matter as we normally connect via anydesk
and so I can introduce the respective command to her.
So it shouldn“t be a problem.
I have to wait for her being availbale though, as she“s a high school teacher and the new school term has just begun. 
Thanks again so much to all of you for your help. 
Many greetings from Rosika 