How to make my prints brighter?

My printer HP Envy5544.
My System MX Linux (Debian 10) with Xfce.

Experiment 1:
I print a pdf page. It contains text an a picture. I only print without colours. After the print I see: The print of this page is too dark.

Experiment 2:
I go to
HPLIP -> HP device manager print settings -> Printout Appearance -> Brightness
I change 100% into 200%

I make a print. After the print I see: The print of this page is still dark. It is not brighter than the print from Experiment 1.
My expectation was, that now the print would be much brighter. I even expected, that maybe with 200% I can hardly read anything.

Experiment 3:
I go to
Xfce settings -> Print settings -> properties -> ...options
There I go to
general options -> more -> brightness

A) My expectation was, that now there I also find the value 200%, as I have changed this value in "HPLIP -> HP device manager print settings -> Printout Appearance -> Brightness".
But there it is still 100%
(???)

So nevertheless I change this value from 100% into 200% too.

I make a print. After the print I see: The print of this page is still dark. It is not brighter than the print from Experiment 1.
My expectation was, that now the print would be much brighter. I even expected, that maybe with 200% I can hardly read anything.

So nothing does behave as expected.
What am I missing?
How can I make my prints brighter?
Why do the settings of
"Xfce settings -> Print settings -> properties -> ...options / There I go to general options -> more -> brightness"
not correspond with ...
"HPLIP -> HP device manager print settings -> Printout Appearance -> Brightness"
..., but are different?

Would appreciate some help.

Thank you.