This article will show you how to set the default PDF viewer in Drive. Whether you want OrbitDoc to be the default viewer or Chrome's preview window.
Note: These instructions apply only for PDFs opened through Google Drive.
For web PDFs, please read How Can I Enable Or Disable Web PDFs From Automatically Opening in OrbitDoc.
To have PDFs to open in OrbitDoc, go to Google Drive and click the Settings button
In the Settings menu, select Settings
In Settings choose Manage Apps
In Manage Apps locate OrbitDoc then check the box next to Use by default
Note: If you do not want PDFs to automatically open in OrbitDoc when in Drive, uncheck the box next to Use by default.