Yes. Circularo provides a full Arabic right-to-left (RTL) user experience. The application has been designed to support any language and content type, not only English or Arabic.
Users can select their preferred language in their Preferences.
You can even use English interface and still be able to send signature requests to external recipients in Arabic (or any other available language) or vice versa.
This can be done by selecting a preferred language in the select recipients step.