Apologies for the delayed response.
Please confirm the exact issue you face when trying to use the "read out loud" option to help us understand the issue better.
Also, mention the exact error if you get any when trying to use the option.
I was trying to use Read Out Loud Tool on my Mobile Phone, But it does not support my Smart Phone.
Also, While working in P.C I was using Adobe and the same tool, it was working fine. I would like to use that amazing feature in my mobile phone.
Sorry for the delay in response.
Read Out Loud feature is not yet available for Adobe Acrobat Reader mobile application.
However, you can use "Talkback" feature in your Android phone settings to read the PDFs.
On iPhone device, you can use the "Voiceover" feature for the same.
You may fill the feature request for this here Feature Request/Bug Report Form
Let us know if you have any questions.