OK so I remembered. Downloaded and extracted it. Not a tool I'm familiar with but it worked fine first time. It's command line so I opened up a command prompt and got this output (snipped a bit as the output was long):

(deck@steamdeck ~)$ cd Downloads/pandoc-3.9.0.2/bin/
(deck@steamdeck bin)$ ./pandoc --help
pandoc [OPTIONS] [FILES]
  -f FORMAT, -r FORMAT  --from=FORMAT, --read=FORMAT                                          
  -t FORMAT, -w FORMAT  --to=FORMAT, --write=FORMAT                                           
  -o FILE               --output=FILE     
  etc......

Does that help?

I see you're coming from windows so how comfortable are you with the command line? I see someone else mentioned that there is a frontend available which might be more useful to you if the answer is "not very".

FYI tab is your friend on the command line as it will autofill stuff for you. So I didn't actually type "cd Downloads/pandoc-3.9.0.2/bin/" I just typed cd Down (tab) p (tab) and it filled it to "cd Downloads/pandoc-3.9.0.2/"

edit: The ./ is essential once you're in the directory when you're running stuff this way. It essentially means "in this directory, run ...". Otherwise the shell will just look in your $PATH directories list and not find "pandoc" anywhere in it. You can add "." to your $PATH to avoid this but it's not there by default on the deck.

Mine is:

(deck@steamdeck bin)$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/bin:/var/lib/flatpak/exports/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl

Last thing - I know you weren't confident picking the right package to download. For binaries you're always looking for stuff with "linux-amd64" or similar in the name for the deck.

There's also a cool little community that you might like called "Linux Upskill Challenge" which you can find at:

!linuxupskillchallenge@programming.dev

It brings you through basics on a day by day basis and on to slightly more advanced stuff as you go.