Add existing PDF ID chat option

gradio_app.py

@@ -117,6 +117,11 @@ with gr.Blocks(title="PageIndex RAG Chatbot", theme=gr.themes.Soft()) as demo:
             upload_btn = gr.Button("Upload PDF")
             upload_status = gr.Textbox(label="Status", interactive=False)
 
+            gr.Markdown("### 🔄 Use Existing Document")
+            existing_pdf_id = gr.Textbox(label="Existing PDF ID", placeholder="Enter existing PDF ID to chat", max_lines=1)
+            use_existing_btn = gr.Button("Use Existing PDF")
+            use_existing_status = gr.Textbox(label="Status", interactive=False)
+
             gr.Markdown("### 🗑️ Delete PDF")
             delete_input = gr.Textbox(label="PDF ID to Delete")
             delete_btn = gr.Button("Delete PDF")
@@ -136,12 +141,23 @@ with gr.Blocks(title="PageIndex RAG Chatbot", theme=gr.themes.Soft()) as demo:
             )
 
     # Event handling
+    def use_existing_pdf(pdf_id):
+        if not pdf_id or not pdf_id.strip():
+            return "Please enter a valid PDF ID", None
+        return f"Set to use existing PDF ID: {pdf_id}", pdf_id.strip()
+
     upload_btn.click(
         fn=upload_pdf_file,
         inputs=[pdf_input],
         outputs=[upload_status, pdf_id_state]
     )
 
+    use_existing_btn.click(
+        fn=use_existing_pdf,
+        inputs=[existing_pdf_id],
+        outputs=[use_existing_status, pdf_id_state]
+    )
+
     delete_btn.click(
         fn=delete_pdf,
         inputs=[delete_input],