You can use Adobe Reader 8.1 or higher to read out text aloud. The text must be in a .pdf file.
First, choose a voice:
Edit - Preferences - Reading
Remove the tick from use default voice and select a voice from the list of voices
Next, switch the reading on:
View - Read Out Loud - Activate Read out loud
Now choose where to read:
Point to the text or choose an option from View - Read Out Loud