Convert Phonegap/Cordova online app to work offline

We currently have an app that is working perfectly using Angular.js, cordova/phonegap, ionic framework. The user of the app logins and receives a number of different questionnaires depending on their login. The user can pick one of the questionnaires and then fill this in and send this data back to the server. Some questions require a photo and/or signature to be uploaded/captured as part the response. All the data calls between the client and server are already developed using JSON. This currently works as an online app however the requirement is to modify the app so it works off line. So we will need persistent storage on the phone, the candidate can chose from : Pouchdb SQLite localForage or other if deemed appropriate Good English skills are essential. There is a full specification available plus the candidate will have the full source code of the working online version and access to a test database.