Hello Oscar,
Thank you for your message.
There are two ways to take screenshots when using mobile Viewer:
1. When connected to a remote Host click on the keyboard icon in the lower part of the screen.
2. Tap on the
Keyboard word in the lower part of the screen.
3. Tap on the
> symbol in the upper left corner of the screen to invoke additional commands list.
4. In the commands list select
Print Scr.
Here's also a reference screenshot:

This way the screenshot will be saved in the remote Host's clipboard - you only need to paste (ctrl+v) it to a file.
Alternatively, you can simply screenshot your remote session on your Android device - this way, the screenshot will be saved to your device's photo library right away. Usually it's possible to take a screenshot on Android devices by pressing the
Power and Volume down buttons at the same time. For more information on taking screenshots of your screen on Android devices please see
this page.
Hope that helps.