Why YSK: So you can easily and digitally write and share mathematics, for free.
I used it for 3 years during my bachelor for many different courses, and I was very satisfied from the variety of choices and outcomes.
Limited to 50 documents and total maximum images upload is 50MB (thanks @cloudless@feddit.uk)
YSK according to its terms of use:
You are limit of creating 50 documents and total maximum images upload is 50MB
Thanks for the heads-up