User Agent

Mozilla/5.0 (iPhone; CPU iPhone OS 12_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.1 Mobile/16B92 Safari/ RDDocuments/6.7.1.567

This user agent belongs to RDDocuments App. This Application run on iOS and it renders web contents with WebKit on iPhone.

Application - RDDocuments App

RDDocuments App

Version? @ 64 bit
Developerunknown
ParentRDDocuments App
Device TypeMobile Phone

Act as 

Crawler No
Fake No
Anonymized No

Device - Apple

BrandApple
ModeliPhone
Platform apple 12.1 (64 bit) by Apple Inc
Mobile Yes
Tablet No

Capabilities

Rendering EngineWebKit by Apple Inc (For Google Chrome, iOS (including both mobile Safari, WebViews within third-party apps, and web clips), Safari, Arora, Midori, OmniWeb, Shiira, iCab since version 4, Web, SRWare Iron, Rekonq, and in Maxthon 3.)
Pointingtouchscreen
Javascript Yes
CSS Yes Version: 3
Cookies Yes
Tables Yes
Frames Yes
IFrames Yes
Background Sounds No
Java Applets Yes
VB Script No
Activex No