Thank you for your response guys!
edubey, I was creating POST request using POSTMAN to test. I will put here later today the command I'm using.
So there is still the challenge to set the metadata for each asset. I did not mentioned before but the goal is not bulk upload but one by one since each PDF file need specific metadata. Even if we can bulk upload all, I sill need the reference to each one to add the required metadata one by one.
I'll think a bit on the options and get back to you on what we applied in case this can be of use to anyone else in the future.
Thank you!