Improving digital signatures, I believe that in the near future this will be a feature that is used much because the tendency is to stop using paper, so the use of alternative mechanisms such as digital signatures (certificates) or (biometrico as tablets wacom) will be one of the features that users will use daily.

Currently the functionality of digital signatures work well, however as a user think it could be improved by including more information regarding errors during the process of signing, suggestions on how to fix some errors in the firms, make more beautiful generally provide more elements tools for firms, even have their own tab with unique tools for firms, for example the possibility of signing with a wacom or surface windows, more information about certificates, mechanisms to enter fingerprint, tablet so there are many possibilities.

Add more options to sign, for example:

Electronic signatures Biometric systems

Sign with wacom signature pad (STU-430, STU-530, DTU-1141, DTU-1031
In Surface Pro 4, sign with Surface Pen.
In Mac OS X using an Ipad and a pencil, draw the signature.
Android using a tablet and a pencil, draw the signature.

Electronic signatures with biometrics (Fingerprint)

Options to enter firm fingerprint using biometric systems.

Digital signatures (digital certificates, PKI)

Option to sign using certificates, extending this functionality by providing more information to the end user as being an unknown subject, the common user does not use this functionality for lack of knowledge and if we add that the environment where you have to sign is unfriendly or usable, loses interest.

Also must provide more information to the user about errors and give you the option or the opportunity to resolve them easily, for example:

As a user I get error messages:

recoverable signature
The selected certificate can not be verified, check the network connection.
recoverable error
Signature recoverable: Unable to verify the signer's certificate. Try again later or check the network connection.

For a common user who does not usually use this feature, when you get these errors simply does not know what you are talking about. Therefore you lose interest or simply stop using it.

manage certificates
Allow to manage certificates, currently only lists them.
Allow to manage trusted entities (certificates certifying entity) or manage the certificate store windows.

Improve usability and make more beautiful signature tools.

Create a tab on the toolbar for the exclusive use of signatures. With all the options set forth above and those that already exist.