Hi.
You can’t decrypt any files in a Cryptomator vault without having Cryptomator locally installed and knowing the vault Passwort and having the encrypted vault files available to the Cryptomator App. This is an end to end encryption.
So you can’t share a file in your vault with someone not having Cryptomator installed.
In fact you cannot share single files in your vault at all.
What you can do is
- share a complete vault by granting access to your online storage and giving away your vault password.
- use Cryptomator hub for working with teams on a vault.
See here Best Practices | Cryptomator Documentation
and here: How do I share files with others?