Deselect All command (Edit menu)

Use this command to deselect any portion of the active document that is selected. The Deselect All command will also remove the column and header lines generated by the user who has activated the Custom conversion selection for a PDF to Excel conversion.

Mouse: Left click anywhere on the document area
Keys: CTRL + SHIFT + A (,), COMMAND + SHIFT + A ()

If this is the currently shown page (everything on it is selected):

After "Deselect All" command is executed, none of the contents of the document are selected for conversion.