Hi @VISHAL_VATS - Glad to hear you are using Coda and the API. To answer your questions:
We don’t have a public roadmap for the API, and at the moment we tend to make additions to it based on user demand, the needs of our partners, etc.
Currently the API doesn’t allow you to directly modify the canvas content of a page, nor does it allow for direct upload of media. The closes workaround would be to have a table with a File column, upload your PDF to some temporary hosting platform with a public URL, and then use the API to insert that URL into the File column. Coda should then read the file from that URL and ingest it into the doc.