To enable or disable OrbitDoc from opening web PDFs automatically, right click on the OrbitDoc icon to the right of the Chrome address bar and then select Options
If you want OrbitDoc to automatically open web PDFs then check the box next to Open Web PDFs.
If unchecked, you can still open web PDFs with OrbitDoc but will require an additional step. The web PDF will open up in Chrome's preview window and an OrbitDoc icon will appear in the top right corner. When you click on that icon the PDF will open in OrbitDoc.
Then click the X to close the screen