Hey Charles good news, the export functionality you need is actually available through the exportAs parameter.
When you add "exportAs": "pdf" to your generation request, the API creates the PDF alongside the presentation. The download URL comes back in the response once the generation completes.
Since you're using Make.com, you can use the official Gamma integration which handles the async polling automatically. Just configure it to include "exportAs": "pdf" in your generation parameters.
The integration will wait for the generation to complete and return the full response including the PDF download URL along with the standard gammaUrl. That download URL gives you the actual binary PDF file - not a webpage - so you can pass it directly to your image conversion step and then to your social planner API.
Check the output from the Gamma module in Make.com - the PDF download URL should be in the response fields once generation completes. Let me know if you're not seeing it and I can help troubleshoot