readme: add warning

README.md

@@ -31,6 +31,11 @@ then modify `/etc/cups/cups-pdf.conf`:
 PostProcessing /path/to/cups-pdf-postprocess-your-wrapper.sh
 ```
 
+*WARNING:* The script does not delete printed files, so files printed through cups-pdf
+will stay where they were printed to (default path is `/var/spool/cups-pdf/${USER}`).
+It is up to you to delete them when needed. Easy way to do so might be to move
+cups-pdf output directory to `/tmp` so it gets deleted on each restart.
+
 To add the script into context menu soft-link cups-pdf-postprocess-your-wrapper.desktop
 into appropriate place for your desktop enviroment (in case of KDE4 this is
 `~/.kde4/share/kde4/services/ServiceMenus`). You may need to copy it and fix path