Level Theta Images is a program that can preserve the vertical orientation of a Theta image even after further editing.
When taking a 360-degree photo (or video) it is usually best to have the camera oriented vertically to make it more comfortable for viewers to view the image in 360. High quality 360-degree cameras have a built in gyroscope in them to allow the image to be oriented automatically. In the case of the Ricoh Theta S, the vertical orientation is recorded as metadata, which allows the image to be correctly presented even if it was originally taken at an angle. However, if you edit a photo from the Theta, the vertical orientation metadata will usually be lost.
Instead of relying on the metadata to correct the vertical orientation, Level Theta Images saves a new version of your photo with the vertical orientation already corrected. That way, even if you later edit the photo, you don't have to worry about losing the vertical orientation metadata.
Level Theta Images is available for Mac and Windows, also requires you to install Hugin, the free panoramic utility. Level Theta Images is free and supported only by donations. Here is the official site.