I can delete pages but how do I delete the file?
Open your file manager. Browse to the folder where the file you want to delete is located. Right-click on the file and select “Delete”.
See also example with Windows:
You can not delete a file using LibreOffice, although you can stop a file from being listed in the LibreOffice list of Recent Files.
To delete a file from your computer you must use your Operating System’s file manager. In many operating systems, simply open the file manager, then navigate to the folder or directory where the file is stored, right-click on the name of the file and choose Delete, or Move to Trash, or something similar.