What are important tricks about saving heavy media files in production?
Here are some tips:

Follow a directory structure similar to this: appname/%Y/%m/%d.
Use AWS S3, or another storage service, for your media and static files.
Compress files to reduce size. 
Use whitenoise, or a similar package, to serve static files in production.

Note: These tips are not solely for media, but also static files.
What should I know about saving files in production? I need to save lots media which are pdf files. The only thing I know so far, is that I shall rename pdf files into my own naming system (for example by overwriting storage in django). But what else is important ?
Or that's all, just saving all files like 1.pdf,2.pdf,3.pdf,4.pdf.. in one media folder and it will work in long term without any other tricks and optimization? I am using django1.8 and python 2.7, but I guess it's very general question regarding running production server at all . 
I hope it's not off topic, as far I faced the lack of information on the issue.