To access the inbuilt accessibility features open the sliding drawer and launch the ATbar (accessibility toolbar).
The image shows the arrow to open the sliding block drawer. You will find the Accessibility block in the drawer. Tap the Launch ATbar button to launch the Accessibility Toolbar.
To use the Read aloud feature in pdf files, you often need to download them and open them with Adobe Reader (opens in new window). You may need to install this software on your device first.
In Microsoft files look for the Immersive Reader feature.