showSaveAsDialog

Shows the "Save As" dialog, letting the user choose a name and a page range for a copy of the current document and then pick where it is written.

If the current document cannot be written in place, the copy becomes the visible document once it has been written, so subsequent edits apply to the copy rather than to the original the user cannot save to. For a writable document the copy is only written; the user carries on with the document they already had open.