I don't think that's an accurate mental model of how a tool like this works.
It's not training a new model on the PDF, or accumulating additional training into its existing model.
Instead, it basically copies and pastes relevant chunks of the PDF into the prompt (invisibly) and then pastes in your question.
It does use calculated embeddings in order to help it spot which are the most relevant sections to use, and it will store those (since they cost money in API calls to retrieve) - but it could be implemented to delete those stored embeddings and the PDF itself when the user stops interacting, or requests that the document is deleted.
It's not training a new model on the PDF, or accumulating additional training into its existing model.
Instead, it basically copies and pastes relevant chunks of the PDF into the prompt (invisibly) and then pastes in your question.
It does use calculated embeddings in order to help it spot which are the most relevant sections to use, and it will store those (since they cost money in API calls to retrieve) - but it could be implemented to delete those stored embeddings and the PDF itself when the user stops interacting, or requests that the document is deleted.