It depends on how advanced you need your text reader to be.
If all you need is VoiceAttack to read out the entirety of a text file you've saved beforehand, or text in a notepad window, you can use the following built-in features:
Read text from fileSet Text [~inputFile] to [C:\test.txt]
Say, '{TXT:~inputFile}'
Read text from notepadSet Text [~prevWindow] to '{ACTIVEWINDOWTITLE}'
Press Left Ctrl+A keys and hold for 0,01 seconds and release
Press Left Ctrl+C keys and hold for 0,01 seconds and release
Display window '{TXT:~prevWindow}' as [Show]
Say, '{CLIP}'
The command target("Send this command to") should be set to "*Notepad".
This will switch focus to notepad for a split second, but unless your VR application uses exclusive fullscreen, or cuts the audio when losing focus, you shouldn't even notice it in the HMD.
Both examples are attached as a .vap so you can import them into VoiceAttack.
Otherwise you'll probably want to look into
VAExtensions, which has functions to retrieve specific sections of text within a file.