Give more details about remote image download

(cherry picked from commit 36a43c2)

Author: cderv

docs/output-formats/pdf-basics.qmd

@@ -271,7 +271,13 @@ SVG format may also have rendering issues such as text clipping in diagrams with
 
 ## Remote Images
 
-When rendering PDFs, Quarto automatically fetches remote image references and properly embeds them within the PDF.
+You can reference remote images directly using URLs:
+
+```markdown
+![Penguins](https://example.com/images/penguins.png)
+```
+
+Images are automatically downloaded during rendering and embedded in the PDF.
 
 ## Citations