Low quality video output using MPEG-4

I have imported a 337 MB mp4 video file into Blender where I am combining it with audio.

You can see my output settings pictured here. When I export the video combined with the audio the file size is reduced to 65.7 MB and the picture quality is much lower, making most of the text in the video difficult to read.

I need to export to the mp4 format. Is there a way I can increase the quality of the rendered video?

What about checking Render size? Is Resolution 100% and set to the same size as in input movie?

Don’t use Blender to render to MP4. Just runder to a high quality format and use MPEG-Stream Clip (free download) to convert to MP4.