SignNow. A very useful tool to sign your documents on the go
I travel two weeks per month and that is a huge amount of time out of the office. Having the possibility to sign crucial documents while traveling is extremely important. It also provides the possibility to have all of them stored and available at one place provided by the application. You don't need extra storage on tour cloud or PC. Once signed, you share it or send it by email from within the application at the same step.
It is multi-platform, I can use it on my smart phone, tablet and personal computer. It also has storage for your signed documents, and of course, you can create folders to be accessed by co-signers.