Absolutely, and that's what I tend to do with my documents IRL, but I think it would be really nice if we could move to a world where signing documents digitally actually meant something more than `signature.png`.
In the EU, in order to have a legal guarantee of being treated as the same as a handwritten signature in all member states, you have to meet "Qualified Electronic Signature" level, which means cryptographic signatures and the involvement of some kind of trust services provider who validates the certificate used to sign. In practice this is rare, and ordinary electronic signatures a la Preview work for most things.
> involvement of some kind of trust services provider
Marketplace at least in the US has shown that once you have this, the actual cryptography really doesn't matter. All anyone seems to care about seems to be "We are company X and have been doing this business for Y years and here's our standard operating policy. We emailed address A at time T1 and the person reading that email address used our online services to electronically 'sign' the pdf P at time T2."
Everyone trusts Adobe/Dropbox/et al to make that claim, nobody cares about certificates and what not.
There does exist a marketplace for documentation to be cryptographically encoded. E.G. Spec sheets. You must have a verified PGP key to open this document, that is generated for a company after they sign a NDA.
In the EU, in order to have a legal guarantee of being treated as the same as a handwritten signature in all member states, you have to meet "Qualified Electronic Signature" level, which means cryptographic signatures and the involvement of some kind of trust services provider who validates the certificate used to sign. In practice this is rare, and ordinary electronic signatures a la Preview work for most things.