Add 'application/pdf' to 'accept' parameter

app.py

@@ -72,8 +72,8 @@ async def on_chat_start():
     # Wait for the user to upload a file
     while files == None:
         files = await cl.AskFileMessage(
-            content="Please upload a Text File file to begin!",
-            accept=["text/plain"],
+            content="Please upload a Text file or a PDF to begin!",
+            accept=["text/plain", "application/pdf"],
             max_size_mb=2,
             timeout=180,
         ).send()