You may either use insight@readdle.com to submit reports or send one right from the app settings. The second way will automatically include the app version you're using in the subject line of the email.
If you report a problem, please provide as many details as possible. We'd also appreciate screenshots, visuals greatly help us to locate the problem.
If you submit feature requests, we would love to hear how this functions would be useful for you and why does your workflow requires it.