If you want to set Chrome Preview as the default PDF reader after adding the Texthelp PDF Reader
Note: These instructions apply only for PDFs opened through Google Drive.
For the Texthelp PDF Reader to not open PDFs from websites please read How can I turn off PDFs from opening with the PDF Reader from websites.
To have PDFs to open in Chrome Preview instead of the Texthelp PDF Reader, go to Google Drive and click the Settings button
In the Settings menu, select Settings
In Settings choose Manage Apps
In Manage Apps locate Read&Write for Google Chrome™ then untick Use by default
Note: Read&Write for Google Chrome can still be used with this option selected - this will only change PDFs to now open in Chrome Preview by default.
PDFs can then be opened with the Texthelp PDF Reader by using the Open with option in Preview and selecting Read&Write for Google Chrome