Signing PDF within Google Drive

[jmbmichael]

We are looking at moving a lot of our forms online utilizing Google Forms and have them saved in Drive as a PDF. That part's no problem but we have several that for instance a teacher fills out and it needs to be signed by the Principal. How are you guys handling things like this? I've been trying to find an extension or app that can easily open that PDF, user signs, then the changes are saved in Drive but I'm coming up empty. All the apps I'm finding are just web services and they all save the pdf on their own storage rather than in the original Drive location. We also have the option to save the files as a Google Doc instead of PDF if anyone has any suggestions on a way to proceed. Thanks for any help.