PDF expert lets you annotate documents, fill-in application forms, add digital signature, manage pages and save documents on the cloud (iCloud, Dropbox). Although you can also do annotation with the free acrobat app but for advanced features, you need to subscribe for £6 a month.
PDF converter – lets you convert pretty much anything to PDF and save documents on the cloud.
You can also employ bookmarklet which enables you to store webpages direclty as pdf from safari and chrome. An alternative way to save as pdf is using Google cloudprint
Scannerpro: Detects borders while you take a scan of a document and has many capabilities which other scanner apps lack.
Documents: File management system for iOS. You can move files back and forth between iPad and cloud servers. The app does not allow transfer between the different cloud servers.
Altamail lets you add reminders, organise folders to establish zero inbox, enables you to add attachments from Google drive and from local folders
