If you are trying to annotate with either the Texthelp PDF Reader Typewriter or Push-Pin tools and text is being deleted when typing with a touchscreen keyboard, the keyboard settings need to be changed
Go to Chrome Settings - type chrome://settings or click the Settings button 
Scroll down to Advanced
Go to Language and input
Under Input method locate your regional keyboard
Click the Open in browser icon to the right as shown below
Under On-screen keyboard click the dropdown for Auto-correction and select Off
This will now allow typing in the annotation tool boxes without deleting any text
