editing PDFs on cloud

I’m looking for a software that I can use on both my phone and laptop to read and edit PDFs. Edit as in highlighting and commenting on text. I want to get away with the hassle of re uploading the PDF everytime I read it and make changes to it. So, I want a platform where I can read them, make changes from any device and it all gets updated every time I edit.

I’m looking for the following specs :

– is free

– Works for android phone and ubuntu OS

– edits pdf and syncs them on cloud