Use Digital Certificate without being installed on the computer

I would like to know if there is any way to use digital certificates in an application without the need for the digital certificate to be installed on the machine. As in the issue of Nota Fiscal, I always use the certificates installed on the machine. Is there any way I can save the file in the Database or elsewhere to be used from any other machine or device?
I've seen some systems use it that way, so you can issue Tax Notes from your phone or from any other computer.
Could you give me any tips on where to start or where to look?