It should not delete the original video file download.
When Jaksta downloads a file it keeps the original download and then creates a new converted file in the designated location (so long as it is set to convert). It makes copy rather than altering or overwriting the original file.
Using the top-left menu go into Jaksta Media Recorder > Preferences > Downloads and it should have the Download location.
You should be able to go to that location and view/play the original downloaded files, as they were before conversion.
You can also go to Jaksta Media Recorder > Preferences > Conversion and set the Conversion location as well.
The Downloaded and Conversion locations should ideally be set in different file locations, if not done so already.
Let me know if you need any further help.
I've downloaded a few videos but when I convert to audio mp3 it deletes the video files...then I have to re download the video file all over again. Is there a shortcut?