If you want to update your training material for multiple courses you have the option to do so, from your Content Library.
Just click on Content from your upper navigation menu and find the training material that you want to update.
Click on the More option, hit Update file and upload the new training material that you want to.
Once you have updated the file, you can now select which are the Courses that need to be updated.
Click on the More option once again but now hit Update Course.
Check the Courses that you want to update with the new training material, click Update Course and you are finished!