Adobe Premiere is a great tool to edit videos, we use it on a daily basis since almost two decades but the H264 encoder of Adobe Premiere Pro could be better as the codec introduces compression artifacts especially at low bitrate.
There’s a free and efficient solution to solve this issue, a video encoder / compressor called Handbrake. The software converts most formats to x264 / x265 and is compatible with Windows, Mac & Linux.
https://handbrake.fr (We are not affiliate, we just think the software is awesome)
This tutorial covers the workflow to follow and the set up of the encoder. We strongly advice to follow along and save the export settings as a preset. The bitrate suggested is the one we use when exporting to our social media, youtube, vimeo and so on. You can increase it if you want to create back up archives for future projects.