Documents Pro contains optional in-app subscription to activate premium services - "1 Month, 3 Month and 1 Year Premium Subscription".
There is also a 7 day free trial for the membership; the free trial period is not transferrable and any remaining free time is cancelled if a paying subscription starts.
Premium subscription adds support for more file types.
Documents PRO is the most comprehensive file manager and mini office suite for the iPhone.
Biometric security features are unlocked by the premium subscription feature.
View and edit many types of files including documents, spreadsheets, photos, and media.
Transfer documents to/from your iPhone via FTP or WiFi, Google, or Email.
No cancellation of the current subscription is allowed during active subscription period.
The price of subscription in local currency is displayed in Extra Features page in app.
Account will be charged for renewal within 24-hours prior to the end of the current period, and identify the cost of the renewal.
Built on top of the acclaimed documents iPhone suite.
Edit & View many types of documents on the fly.
Easily copy and share files using WiFi, dropbox, SkyDrive, and Google Docs.
Subscriptions are auto-renewable and can be cancelled through User Account Settings.