Best way to add subtitles to videos I currently have ~200 short 30 second teaser youtube video that link to articles. 

I am looking for the best way to add captions to these videos. These will eventually go out on social media. Because the videos are short and clear, the youtube default captions are actually quite good. 

However, I want the captions to be part of the mp4 file so that when I share it on social networks (uploading the video directly) then the captions appear. 

What is the best way to do this? This is the ideas I have so far: 

1) I could manually download the captions for each video, then use some service (which one) to merge the captions with the videos, and then post it. 

2) I could download the captions for each video, then use the social networks service to add the caption as an add-on, you can do this with fb at least. The downside of this is that it would have to be done again and again for each social network. 

This is for a volunteer run non-profit so there is no money to get this stuff done with super expensive software (though we have the adobe suite including premiere). 

Any thoughts would be greatly appreciated!
1) Is probablly the easyest. You can download it from YouTube and merge it in Premiere Pro. Easyest way is to burn it in, so you wont have any struggles with other social media plattforms.

If you have basic programming knowledge, ypu could write a script whoch automatocally downloads and adds the sub titles from YT.