How can I upload/attach file like PDF in Google Gemini AI API ? (Model Gemini 1.5 Pro)

Question

I have two questions,

1. How can I upload/attach files like PDF in Google Gemini AI API? (Model Gemini 1.5 Pro or any that support file attachment). Also, if this doesn't support, is there any better alternative, maybe like Vertex AI or any Azure or any AWS AI etc.?

2. I want to know how I can track usage of API keys created on Google AI Studio?

I tried research and implementation from the official docs like https://ai.google.dev/tutorials, but didn't get anything yet, that I'm looking for.