If you need to void a checklist you can do this under the Checklists tab within appropriate transaction. Select the checklist you need to void. After that click Action button and select Void Checklist. You can then rename the voided checklist to identifies it from the rest of the checklists.
All documents that were uploaded before voiding the checklist will be saved. Any incomplete tasks will be deleted and notes made on those incomplete tasks will not be saved.